ML23251A024
| ML23251A024 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/2023 |
| From: | NRC/OCIO |
| To: | - No Known Affiliation |
| Shared Package | |
| ML23251A034 | List: |
| References | |
| FOIA-2023-000163 | |
| Download: ML23251A024 (1) | |
Text
t i
d MAIN TRANSFORMER -
REPORT FOR EVENT OF AUGUST 13,1991 Prepared by: Steve Dotv h Date: September 7.1991 Gl7,0 s O File Code: 82801 788'288?!3sa88ho 8 PDR
4 2MTX XM1 B FAILURE A full evaluation of the 2MTX XMIB failure is underway. The areas that are being evaluated are as follows:
A. Environmental Impact -
B. Transformer Testing C. 345KV Switchyard Work D. Trending Data E. Root Cause Analysis F. Material Submitted to the NRC l G. Restart Plan and Sampling Attached is a preliminary evaluation of each of the above categories.
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ENVIRONMENTAL IMPACT -l
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i On Aug.13,1991, the Director of Environmental Protection, Hugh Flanagan, was notified of the oil spill on transformer 2MTX-XM1B. The New York State Department of Environmental Conservation was notified at 12:05 p.m. which was within the required two hour notification limit. A courtesy notification was made to the National Response Center at 12:52 p.m. on 8/13/91. ;
The storm sewers, oil separator and visual observation of the lake revealed no oil had <
leaked to these areas. A small amount of oil had sprayed outside of the transformer containment pit. The stones and small portion of dirt have been removed and are waiting to be properly '
disposed of in cooperation with the DEC. The oil (approximately 400 - 500 gal.) that remains within the transformer containment pit is planned to be removed; however, there is no urgency. ,
The oil separator will function as designed with the oil in the pit. The oil within the pit does .
not pose an environmental or fire hazard.
Ten-twenty gallons of oil was spilled Sunday, August 18,1991 in the afternoon. ' Hugh ,
Flanagan was notified by Tim Kurtz at 5:25 p.m.. At 6:00 p.m., Hugh Flanagan reported the :
spill to the New York State Department of Environmental Conservation. The spill has been ;
cleaned up and is waiting to be properly disposed of in_ cooperation with the DEC. j i
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TRANSFORMER TESTING RESULTS l
l The 2MTX-XM1B transformer has been tested. The preliminary evaluation of the testing indicates there was a significant low voltage winding failure. The transformer appears to be a total loss. The lack of copper splatter on the top of the windings leads the transfonner l consultants (G.E., Stone & Webster and McGraw Edison) to believe there wasn't any apparent high voltage winding failure. The failure has caused distortion of the tank, windings and bus structure within the transformer. Based on the relay scheme, the fault originated on the high side of the transformer. See the Electrical Distribution Report for further clarification.
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The following tests have been done on Phase A, C, and D:
a) Doble Test b) Meggar of Windings: Core to Ground c) Turns Ratio Testing The testing does not indicate any degradation within the transformer. The Meter & Test
. Department has compared the testing result from 1985 to the present and has concluded that the equipment is in satisfactory condition. The test results are attached.
The oil analysis comparisons, over the last year and after the failure, support the preliminary evaluation that the oil analysis did not lead to any precursor to the B transformer failure. The increase of Mehtane, Ethylene, Ethane and Acetylene are indicative of a large amount of arcing inside the B Transformer. After review of the past oil analysis, the transformer consultants concur there wasn't any warning signals of the failure.
The absence of a precursor is not unusual for the type of failure indicated by the physical damage. At this time, we are not able to suggest a root cause for the transformer failure. l l
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i 345KV SWrIUWARD WORK :
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l The 345KV switchyard work schedule is progressing very well. Attached is a chart of our l recovery plan. The work chart should be self explanatory. We are testing All of the main transformers and the house service transformer to new installation standards. The transformer 2MTX-XM1B was removed from the 345KV switchyard on 8/22/91.
The bids are out to various vendors who will perform repair and a root cause evaluation.
Niagara Mohawk will be involved with the root cause evaluation.
The isophase was meggar tested on 8/21/91 and a PI test was performed. The test results were satisfactory. A visualinspection was done on portions of the isophase that were accessible.
No problems were noted.
The tap changers on each of the transformers were exercised. The Doble Tests and Meggar Tests indicated the tap changers were in satisfactory condition. No other testing of the tap changers is necessary.
The Electric Operating Procedure, EOP-401A, titled power transformer checklists before energization and after energization, were performed on the 'D' Main Transformer. All tests and i inspections were satisfactory. Data sheet attached.
1 The main step up transformers, 2MTX-XM1A, XMIC, XMID and the House Service Transformer,2STX-XNSI were backfed from 8/26/91 thru 8/30/91. Gas in oil samples were taken every twenty-four hours. The results were satisfactory.
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MAlki TRNJSFORMER RECOVERY PLANI Bio 3I9l 81I4/91 8185198 SitGl91 8183/98 8/9919l 8/20191 Blit[9 t TUES WED THURS rRE SAT SUM Mohl TUES WED HAMG IMSTALL MARK UPS 6R00MDS C- ------- - - ^
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U ELECTRIC OPERATING PROCEDURES w g
17 D* 2/15/90 SUBJECT INSPECTION, INSTALLATION, TESTING & SECTION STORAGE PROCEDURE FOR NEW AND REBUILT STATIONS TRANSFORMERS & LTC'S VIII. INSPECTION AND 5. A portable oscillograph shall be used to obtain a TESTING BEFORE record of appropriate currents and voltages of tne ENERGIZATIO'i initial energization and deenergization of power
( CONT' D) transformers 12000 KVA (OA) and above.
- 6. Check and confim that all protective relays'and alam circuits are operative.
- 7. Check and confim that calibration of all temperature and pressure gauges has been performed; also that calibration and proper functions of thermostatic control-systems for cooling fans and oil pumps has been perforised and recorded.
~
PRECAUTION: Extended operation of cooling pumps '
in the manual mode is not reconssended due to possible effects of static electrification' phenomena. Refer to manufacturer's recossaended sequence for manual pump operation and settling times. This must be observed prior to energization of transformer to prevent possible failure of' the transfortser.
For rebuilt or relocated power banks with 2 stage FOA cooling (230 KV and above), refer to E0P 401, section IV-8.3 for oil fill operations and pre-energization details.
i
- 8. Perform the following tests prior to energization (see Tables 1 & 2, E0P 401). I
- a. Dissolved Gas and Quality Index tests on main tank oil,
- b. Dielectric test on LTC compartments (after ;
. performing external . inspection). '
- c. Perform Power Factor Test. I S
i ~ *
$ SYSTEM STATIONS SYSTEM ELECTRIC q g 9/1/87 AND HYDRO DIRECTOR OPERATING C0044ITTEE i j
E0P 401A Page jg of ELECTRIC OPERATING PROCEDURES )7 Date 2/15/90 SUBJECT INbVLLlLUN, ANd4ALLAiAUN, IUIANU 5 SECTION STORAGE PROCEDURE FOR NEW AND REBUILT STATIONS TRANSFORMERS & LTC'S VIII. (Cont'd) i TBi turx-Ym,3 POWER TRANSFORMER CHECK LIST BEFORE ENERGIZATION Sheet 2 of 4 CHECKS TO BE MADE CHECK INITIALS
- 12. Touch up all scratches or minor abrasions to the transfomer paint. M $
- 13. Check all terminal connections in the control cabinet for tightness.
[ g,/f[
- 14. Check the operation of the breather (s) for the conservator tank and LTC where equipped. Check / ,
the dessicant material condition (dark-blue ,/ pT,7 color) when used.
- 15. Perfom " internal inspection" of LTC switch mechanism (s) and operation of contacts. Vacuum interrupters should be "high potted" to verify acceptable vacuum media. Nh /M 4
- 16. Check coolers / radiators for debris ,/
accumulation or obstructions. V 40
- 17. Bleed the gas detector relay, if so equipped. g
/
- 18. Check / verify operation and calibration of hydrogen gas monitor, if so equipped. MgJ- /d7#-
- 19. Energize control cabinet heaters.
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- 20. Check / verify that all relays, including trans-fomer differential relays are in service. gfff 21 . Check / confirm that temperature and pressure instrument calibration was perfomed and recorded.
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I super o. Document osted l Authoriz.d By Approved By SYSTEM ELECTRIC
{ 9/1/87 AND HYDRO DIRECTOR OPERATING C0ffilTTEE
N3"M , ELECTRIC.0PERATING PROCEDURES
- co" *o'^
- 8' 13 '
17 D2/15/90 SUBJECT INSPECTION, INSTALLATION, TESTING & SECTION STORAGE PROCEDURE FOR NEW AND REBUILT STATIONS TRANSFORMERS & LTC'S VIII. (Cont'd)
TBf xm7x-xeo POWER TRANSFORMER CHECX LIST BEFORE ENERGIZATION Sheet 4 of 4 CHELKS TO BE 14ADE CHECK INITIALS
- 30. For transferners with dual station service auxiliary power, verify automatic transfer g functions. M 31 . Refer to E0P 15 for additional requirements /
prior to energization. V //Fr,
- 32. When the results of the tests are obtained, they shall be a permanent part of the test data that follows the transformer throughout its life.
[ Np Supervisor's Signature [ ~
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so m oocum.ni o.tw A m w sy Am #
~ 9/1/87 AND HYDRO DIRECTOR
- OPERATING C0mIT1TE l - . . .
i N3" M ELECTRIC OPERATING PROCEDURES
- '^
"15 '
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17 D 2/15/90 SUBJECT INSPLGIION INSIALLAIIUN, i L5 I Inia & SECTION
- STORAGEPR6CEDUREFORNEWANDREBUILT STATIONS TRANSFORMERS & LTC'S i
IX.
l TBf 2mrx->vno POWER TRANSFORMER CHECK LIST AFTER ENERGIZATION Date f"[z s, di Serial No. Co(40 7-f4 Mfg. /he. 6A EbiScut)
Voltage Primary 2V '3o o Yoltage Secondary 3 YCraoc) M.V.A. #c)Y Location M/U /* t Date of First Energization 7d44/ [hrerd CHECK 5 TO BE MADE CHECK INITIAL 5 When the results of the tests-are obtained, i they shall be a permanent part of the test '
data that follows the transformer throughout ;
its life. '
- l. Voltage checked at each load tap changer posi-tion (when applicable). //[4 ' /M
- 2. Operation of gauges, gas monitors, etc., checked. [ /ff l
- 3. Verify operation of alarms, thermostatic controls, and protective devices. [ /M 4 Combustible gas analysis made (Optional).
- 5. Dissolved gas in oil test made.
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- 6. Check for Hot Spots, Oil Leakage or other abnormal occurrences.
y g Supervisor's Signature 'b -
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,, Supersedes Document Dated Authorized By ^
SYSTEM STATIONS SYSTEM' ELECTRIC' N
9/1/87 AND HYDRO DIRECTOR OPERATING C0lWITTEE
l
. i N E0P 401A ELECTRIC OPERATING PROCEDURES "'" 17 17 D 2/15/90 SUBJECT INSPECTION, INSTALLATION, IL5 TINEA & SECTION STORAGE PROCEDURE FOR NEW AND REBUILT STATIONS TRANSFORMERS & LTC'S XI. TRANSFORMER 1. General - When accessories are not mounted ACCESSORIES immediately efter the transformer is received, tney STORAGE must be protected from damage or loss. The following instructions are general; more detailed instructions are given in the manufacturer's manual. 1 1
- 2. Radiators and Coolers - Store in such a manner that l water or moisture cannot stand on sealed ends. l
be stored with the top end elevated at an angle of j 20". '
- 4. Fans - Store indoors. If storage exceeds one year, l j
operate periodically. If mounted on radiators, they !
are not to be left outdoors for more than eight (8) weeks.
- 5. Pumps , Pump motors must be kept off the ground and protected from the weather. These pump motors may be stored outdoors for three (3) months. If a longer storage time is required, they must be stored indoors.
6.
Miscellaneous Item - These items should be stored indoors and in a dry place. These items would be !
gaskets, connectors, tape, paint, etc.
NOTE: These instructions specify minimum requirements necessary to assure that the i transfonner and its accessories will be handled without violating the manufacturer's warranty. For more detailed instructions, refer to manufacturer's instruction manual i
and the Niagara Mohawk " Guidelines for Proper '
Care of Power Transformers Prior to Energization."
E i Supersedes Document Dated
. Authorized By Approved By C
SYSTEM STATIONS SYSTEM ELECTRIC 3 9/l/87 AND HYDRO DIRECTOR OPERATING'COM4ITTEE
TRENDING DATA The initial trending is still underway. The areas being trended are the:
- 1. Electrical Department Daily Yard Readings.
- 2. Operator Daily Rounds.
- 3. Quarterly Oil Analysis.
- 4. The work that has been perfonned over the history of the transformer.
The initial evaluation of these areas is not leading us to a precursor for the transformer failure.
Attached is a progress report for each of the above.
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1 The Electrical daily yard readings have been trended from 8/4/91 through 8/13/91.
. The Phase B winding temperature over the 10 day review is less than or equal to 80*C which is below the 105*C Control Room Alarm initiation and procedure acceptance criteria. The Phase B oil temperature is less than or equal to 60*C, which is below the 75'C acceptance criteria.
The Control Room Alarm initiates at 90*C. The evaluation revealed no apparent sudden temperature rises in the windings or oil up to point the transformer failed. The oillevel indicator over the 10 day review was normal. The indicator did not read high or low. The gas volume indicator was not in the red zone. The pressure relief devices had not been initiated until after
- the transformer failure. The bushing oil level was satisfactory. The Fan Banks,1 and 2, were in operation; this is not unusual given the time of year. AT 75*, the second. set of fans is started and the second pump is started for additional heat removal capability. All of the individual fans were in operadon on Phase B. All of the oil pumps on Phase B were in operation.
At the time we encountered a fault on Phase B, the trip releying automatically sheds the pumps and fans. This explains why the Operators and Damage Repair Teams did not see the fans or pumps in operation. The Phase B lightning counter was reading 0. The inspection of the Phase B cabinet for cleanliness and operation of the heater were satisfactory.
The same parameters have been reviewed on Phases A & C as the parameters reviewed on Phase B. The data does not demonstrate a differential in the reading between the three (3) transformers. The only abnormal reading is on Phase A. Phase A was struck by lightning on the week of 8/31/86. The initial evaluation of the lightning strick does not tie together with the Phase B failure.
The operator daily rounds have been evaluated from August 6 through August 13,1991 for any lead to the transformer failure. The components monitored by the operators are bushing oil level, transformer high pressure relief valves and transformer oil levels. There is nothing within the operator daily rounds that leads to the transformer failure.
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WINDING 1EMPERARIRE 2MTX XM1 A-B-C DAY DATE PHASE A PHASE B PHASE C Sun. 8/4 85*C 75'C 85'C Mon. 8/5 88'C 77'C 84*C Tues. 8/6 88'C 77*C 84*C Wed. 8/7 84*C 74*C 84*C '
Thurs. 8/8 84*C 75'C 85'C Fri. 8/9 80*C 71*C 80*C Sat. 8/10 90*C 80 C 85'C Sun. 8/11 90*C 80*C 88*C Mon. 8/12 88*C 79*C 88*C Tues. 8/13 71*C Fault on B> 180*/58*< Returned 65'C to the value after the Fault 4
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OIL TEMPERATURE ON 2MTX XM 1 A-B-C DAY DATE PHASE A PHASE B PHASE C Sun. 8/4 69*C 55*C 65'C Mon. 8/5 65'C 58*C 61*C Tues. 8/6 65'C 59'C 61*C Wed. 8/7 62*C 55'C 61*C Thurs. 8/8 62*C 55*C 60'C Fri. 8/9 59*C 52*C 57*C Sat. 8/10 64*C 59*C 62*C Sun. 8/11 68'C 60*C 62*C Mon. 8/12 66*C 59*C 64*C Tues. 8/13 62*C 87* Mar / 58* at point 65'C when yard readings taken
!- i
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A review of the oil analysis from June 1 to August 14,1991 has been done for 2MTX XM1 A, B, and C transformers.
The review does not lead to a precursor on the 2MTX XMIB transformer. The review was conducted by Charlie Raymond, a consultant from General Electric. The Ethylene, Ethane, l
Methane, and Acetylene were found to be at normal levels. Harold Light from the Niagara Mohawk Standards Engineering Group concurs with the General Electric findings.
2MTX XMIC Ethane (C2H6) concentrations were found to be high. The Meter & Test Department and Chem Lab were consulted and found the Ethane (C2H6) concentration to be of l no concern compared to the other gaseous concentrations within the transformer.
The absence of an oil fire is theorized to be from the lack of oxygen levels and the temperature of the oil did not reach the ignition point for a long enough period of time.
l
2MTX X1M1 A.B. AND C Methane CH4 <160 ppm required Acetylene <11 ppm required A B C A B C 5-1-90 44 5-1-90 0 7-30-90 58 7-30-90 29 7-30-90 116 7-30-90 0 7-30-90 0 7-30-90 0 12-3-90 46 12-3-90 37 12-3-90 92 12-3-90 0 12-3-90 0 12-3-90 0 2-21-91 60 2-21-91 34 2-21-91 117 2-21-91 0 2-21-91 0 2-21-91 0 5-29-91 136 5-29-91 48 5-29-91 126 5-29-91 0 5-29-91 0 5-29-91 0 6-20-91 54 6-18-91 111 6-20-91 4 6-18-91 0 6-21-91 77 6-21-91 0 6-21-91 63 6-21-91 0 8-14-91 92 8-14-91 155 8-14-91 0 8-13-91 4607 8-14-91 0
2MTX X1M1 A. B. AND C t Ethylene C2H4 <190 ppm required Ethane C2Hs <115 ppm required A B C A B C
[
5-1-90 10 5-1-90 40 7-30-90 11 7-30-90 8 7-30-90 17 7-30-90 49 7-30-90 19 7-30-90 145 12-3-90 15 12-3-90 17 12-3-90 23 12-3-90 48 12-3-90 31- 12-3-90 128 ;
2-21-91 0 2-21-91 0 2-21-91 53 2-21-92 53 2-21-91 23 2-21-91 189 5-29-91 0- 5-29-91 31 5-29-91 33 5-29-91 52 5-29-91 49 5-29-91 177- ,
6-20-91 0 6-18-91 31 6-20-91 -63 6-18-91 161 0
6-21 6-21-91 63
+
6-21-91 0 6-21-91 53 4
8-14-91 0 8-13-91 12287 8-14-91 0 8-14-91 68 8-13-91'3120 8-14-91 204 I
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I i The Work Tracking System was reviewed for reoccurring problems over the history '
of the transformer. The review has not lead to any information as to the failure of the B Phase Transformer. The minor maintenance ~ items that reoccurred are: 1 j
- 1. The cooling fins have been blocked by debris and required cleaning.
- 2. Small oil leak, which were repaired. .i
- 3. Loosening of bolts from vibration, which have been retightened.
A computer printout of the WRs is within Attachment 1.
The Engineering Department reviewed .the vendor manuals to reassure the procedures' are following the vendor's recommendation. Attachment 2 contains the documents reviewed with the results from Engineering.
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s e Display of Work Item Data SEEK Strategy COMP I D=2N r x - a n t t#, At4D W81HHip) u sort fieldt C Off DA T E HIT I Work No Wl62321 Status O Work Item Descriptiott TRANSrORNER 2 NIX-RNID I A l tJ D C AUS] tig GAS Cl til R A1 ]ON OVT'R PHESSUR IZ ATION AND OIL LEAKACE. PERFORN lta5PEC1 tuta 10 DE TFitMint' C AUSL Of F All efPE At3D HEPAllt 14! T 2 Work No W162321 Status. O Work Item Desertption TRANSVORNER 2 NIX KNIO FA ll I.D CAUSitaG C AS Of f 4ER A T IOt4 OVFR-PRESSURIZATION AND OIL LEAKAGE. PERFORN It4SI'E c t lON 10 DETIRNltlE LAUSl Of F All.URF: AND REPAIR HIT 3 Completion date 860804 Work No WlOl277 Status C
, Work Item Descraption 2MTX-xNip. 345 kFMR 10. COOtER tlANK 1.
RUNNING DUTION F AN ON COOLER 1 FAN DANK HAS AN OCCASIONAL VIBRATION WHEN Corrective Action t40 CORRECTIVE ACTION NEEDED. LLECTRICALLY RAN COOLER DAtJK NO 1. NO APPARENT PROBLEM FOUND ON BOTTON FAN NO 1 Cause of Failure t40 F Alt t1RE F OUND AT THIS TIME HIT 4 Completion date 870s2O Work No W120967 Status C Work Item Deseraptaon TRANSFORNER OIL AT HASE OF UNIT Corrective Action Cause of failure NO FAILURE tiO O t t LEAK DETECTED. USED CRC AND HACS TO REMOVE TRACE DEL AND WATER FROM AROUND BASE OF TRANSFORMER HIT 5 Completion date. 870019 Work No W120663 Status C Wor 6 Item Description REMOVE APPROPRIATE ALL RUST ANDCOLOR PAINT AND L OOSE PAINI FROM THE SURFACE OF Tile 345 KV TRANSFORMERS AND PAINT THOSE AREAS WITH T Cortective Actaon CLEANED RUST SPOTS AND PAINTED DOTH PRINER At40 OVERLAY Cause of failure WEATHERING OF TRANSFORMERS HIT. 6 Completion date 800128 Work No W120796 Status C Work Item Descriptaon HOT SPOT.
ANDER CAPS PUSH TO TESTAND (93-20-304) DUTTONS. ( ENS COVERS ARE DROMEN NEED TO DE REPLACED (CATALOG NO BOOT-N42) NEED 3 3 RED CAPS Corrective Action REPLACED ALL LENS Cause of failure PRESS!NC 'O HARD Utd PUGH DUTTONS HIT 7
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a Dt9plog of Work Itom Dat.s SEEM Str.ategg f.OMP i p 2rtl s v Mlli. AND txistesso is Sort fields C OMP DA T C HIT 13 Completion d ,s t e anilly Work No W137146 l Status C Wort Item Danceaption CHECM cal.IDRAllON Uf W i t ID illG I EllP[ R Allfl#E IllD I C AT()R ON EAST SIDE OF 2MTX-XMID. IT INDICATES GREATER THAN 30 DEC C HI GitF H T HAta W lf1D I NG IFMPH ON Olt tt H MAIN t il ANSFOR MER S. FOLLOWING LAST RM STARTUP. TEMPERATURE REMAINED AT 76 DEG C EVI N DIM 4ING SHUIDOWil Corrective Action RECALIDRATED TEMP SW11CH PI'R LCR IL2GPM-022. INDICATOR AND SWITCH SETPOINTS READINQ CORRECTLY Cause of fatture TEMPERATURF INDICATING SWITHC SOUND READING LOW. DUT SWI TCH SET POINTS WERE ADOUT 5 DEGREE C HIGH HIT 14 Completion date 890981
/,
- Work No Status W159306 C
Worn item Descraption OIL COut ERS HAVE !)IR T ACCUMUt.ATED ON DACM SIDE PLEASE CLEAN Cor r ec tive Actson DRUSHED OUT ACCUrH IL A T F D Dt mi AND DE DR I S F RON SupFACE AREA OF COOLING FINS. MORE EXTENSIVE CLEANING PLANNED FOR UUTAGE Cause of failure NORMAL ACCUMULAllute HIT IS Com'pletion date 890919 Work No Wl59266 Status C Work Item Description INSPECT NLUTRAL RUSHING CONNECTIONS ON MAIN TRANSFORMERS FOR POSSIDLE CORRCSION OF CONNECTIONS Correttive Action. INSPEC TED NEUTR AL DUSHING CONNEC TIONS ON MAIN TRANSFORMERS AND FOUND NO PROBLEMS HIT. 16 Completion date 890920 Work No W159274 Status. C Woch item Description INSPECT WHERE DOS AND TRANSFORMER JOIN (CilECK FOR LEAKSI Correttave Actaon SEALED DUS CONNECTION WITH HTV SILICONE HIT 17 Completion date 890922 Work No W159227 Status C Wort item Description TRANSFORMER IS LEAKING F ROM PLUGS LOC ATED ALONG THE SIDES ALEASE CLEAN AND MAKE TEMPORARY REPAIRS TO PREVENT PL UGS FROM L EAMING Cortettive Action SEAL EO At L PLUG LEAMS HIT 10 Completion date 898209 Wort No W147616 Status, y Work Item Description TRANSFORMER OIL T E' MP INDICATOR APPEARS TO DE STUCK REPAIR CALIBRATE OR REPLACE Correc t a n Action CLOSE THIS WR - IT IS A DOPLICATE OF WR 158186 STILL OPEN. VOID Cause of fa6 lure DUPLICATE WR
'l . .
Displag of Wor 6-Item Data SEEM Strategy cnMP I D=2MT x- a fil H. AfW WOWNO7W
, sort Fields C Ot1 Pila TI' HIT 19 Completion date 9002OH Work No . W15923S '
Status. C Wara item Descriptson MA18E FANS 2UP ANDt INST PUMP PUMP ALL 2 NAME Pl. ATES FOR FAN AND PUMP CONTROL IN CONTROL CABINET I BY 2 IN SIZE EAVING FANS 1 Correctave Actaon INSTALLED NAME PLATES I DE NT IFY INC . F AN/ PUMP AS APPLICADLC Cause of failure F AN/ PUMP UNI TS CON TROL L ER NO T IDEN T IF IED HIT 20
. Completion date 900307 l Wort No W175907 j Status. C Work item Description-i- Corrective Action !)OORS ON THE SODE Or 1HE TRANSFORMER DO NOT ST AY CLOSED NEED TO REPAIR OR REPLACE
'ADDED STOP TO DOOR 10 STOP F ROM OVER T H AVf' t.
Cause of failure DOOR WOUt.D NOT t.ATCH CORRECILY
.. HIT. 21
. Completion.date., 900322 Work No ,
Wil9692 Status. V Work Item Description NOISE AND VIDRATION APPEARS 30 DE Car 11NC FROM NO !. COOLER ON D 0 OF MAIN TRANSFORMER IN THE 345 SW YD. CM '
AND REPAIR AS NECESSARY f Corrective' Action. NO WOFM REGUIRED NT M-XM t B HAS TIEEN PREVIOUSLY REPAIRED - WR ' 162932 WILL REPAIR MTX-XM1A HIT. ' 22 Completion date 901103 Work No W179185 Status. < C Work Item Description. TRANSFORMER DIL.LEAMING FROM OIL PLUCS SEAL AS REQUIRED.
, Corrective Action RESEALED OIL PLUCS WITH DURA METAL AND POINTED AREA WHEN DRY. ,
HI T. -23
! Completion date. 901307 Work No.- :W164938 ,
i Status. V'
- . Worb item Description.
DOTH LEAD AND LAG COOLING SYSTEMS ARE RUNNING (TAKING LAG TO OFF THEN AUTO -!T RESTARTSI 1 B'S WINDING' HOTSPOT" TEMP IS 10 DEC. C LOWER THAN 1A AND IC WHICH HAVE ONLY LEAD COOLINC SYSTEM Rupe4ING Cortective' Action WORK DONE ON WR 16997I l HIT . .
24 h Campietion date. 901114' Work No. . Wl64939
- Status. . . V. '
3 Wort. Item Description.
BOTH LEAD AND LAC COOLING SYSlEMS ARE RUNNING (TAKING LAC TO OFF THEN AUTO -IT RESTARTS) 1 B'S WINDING
- Corroc tive At tion HOTSPOT TEMP IS 10 DEC C LOWER THAN 1A AND IC WHICH HAVE ONLY LEAD COOLING SYSTEM RUNNING WORK PERFORMED DY SUPPORT DEPT HIT. 25 5
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Display of Worb Item Data SEEK Strategg COMP I D=2M T x -- s M I D . AND WORKilOeW Sort 7ields COMPDAIE i
'o Comptetnon d .* L e Work No 901206 W169974 f f i,. *t g m i s'l / (
Status C .-
Work Item Descriptson DOTH (OOLINC (AN H AHMS 140NN IN( WITH HOT SPOI TEMP CONSIDERADLY BELOW THE SETPOINT 75 DEGREES C FOR PICMUP
, Or THL SECONp F AN DAHM (NVESTICAIE PRODILM WITH HOT SPOT THERMOMETER DEVICE 49 AND REPAIR.
Corrective Action g FOUND TIS DAD REPLACED IIS AND cal.lDRAIED OIECMLD 1.OOP Cause of failure ' TIS 
LD NOT CAL HIT. 26 Completion date 901207 Worb No W169975 Status V Wort Item Description DOTH COOLINC FAN DANKS HUNNINC WITil HOT SPOT TEMP CONSIDERADLY BELOW THE SETPOINT 75 DEGREES C FOR PICMUP OF THE SECOND FAN DANK INVESTICATE PROULEM WITH HOT SPOT THERMOMETER DEVICE 49 AND REPAIR.
Correttave Att on NO WORK REQUIRED HIT 27-Completion date 910322 Work No . W161359 Status V Work Item Description LEAM IN PIPE JOINT ON FIRE PROTECTIOt4 SYSTEt1 AROUND TRANSFORMER-LEAK IS IN SOUTHEAST CORNER j Correttive Attion NO WORK REOD WORK WAS DONE ON WR $57435-HIT 28 Completion date, 910325 Work No W161359 Status. V Work Item Desertption LEAM IN PIPE JOINT ON FIHE PROTECTIOte SYSTEM AROUND TRANSFORMER-LEAK IS IN SOUTHEAST CORNER Corrective Action -SEE LEAD HIT 29 Completion date. 910401 Work No Wl58106 Status C i Work Item Description DEF TAC 10790 TRANSFORMER WINDING TEMP INDICATOR APPEARS TO DE STUCK AT 52 DEC C. TROUBLESHOOT IDIL TEMP READS 12 DEC C.1 ._
Corrective Action 2SPM-TISIO490 WAS READ ON 910331'AND IS READING APPROXIMATELY THE SAME AS THE INDICATORS FOR XM1A XMIC AND (YHiD 'ALL OIL AND WINDING TEMP INDCIATORS ARE READING APPROXIMATELY 10 DEGREES C ISO DECREES F) WHICH COES
- ALONG WITH OUT SHUTDOWN STATE ON THIS DATE HIT . 30 Completion date 910405 Work No. W193930 Status. C Wark Item Descript on DURINC WARN WEATHER TO BE PLACED IN HAND CONDITIGN rAN 1 DID NOT AUTO START WlTH THE CONTROL SWITCH IN AUTO. CONTROL SWITCH HAD Corrective Actnun Cause of Fanlure-
~
(REPLACED VOLTAGE DROPINC RESISTORS ~ L- p g ,.gs - g ;,g,g 3 RESISTORS OPENED
}
i l 1NTERNAL CORRESPONDENCE M Y NIAGARA Fonu 112 2 Q 02m 55 01 013 gy
, -FROM DISTRICT Anwar Qureshi Nine Mile Point Unit 2 DATE August 20, 1991 FILE CODE NMP77862 Steve Doty SUBJECT Event Assessment, Technical Manual Review /
Vendor Information 2MTX-XM1B We have reviewed the following documents for Main Transformer 2MTX-XM1B.
- 1. Instruction Manual #649, NMPC File No. N21033 l 2. Instruction Manual #C06607-5, NMPC File No. N20445
! 3. N2-EPM-GEN-R700 l 4. N2-EPM-GEN-Q692 l 5. S-EPM-GEN-V060
- 6. N2-EPM-GEN-D0690
- 7. One line diagrams EE-1A, B, C, M01F, M01G
- 8. FSAR Section 8.2.1.3, Page 8.2-3 I
our general review of these documents do not indicate any l conflicting requirements for the maintenance and testing of the l Main Transformer. Above referenced EPMs seem to be adequate per the vendor manual requirements.
- Please contact myself if you have any questions or need additional information.
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]i.).;W' b4 f,W/N n
0< si Anwar Qureshi -
Site Engineering - Unit 2 AQ/bm xc: Paul Mangano Rick Abbott Records Management NMP PPF l
l
3 ROOT CAUSE ANALYSIS The Quality Assurance Operations Group has taken the lead to perform a Root Cause Analysis of the 2MTX XM1B failure. They have gathered information dating back to the point that the transformer arrived on site. i They also have contracted Doctor Chei's Consultants Team _to help with the Root Cause Analysis.
3 1
The Root Cause Analysis may take some time before they arrive to any l conclusions considering the transformer. has to be shipped off' site for the-l evaluations. Attached you will find the' Root Cause Analysis format and some of the data-already gathered.
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. . - , _ . . - _..-_.~a..-.-2. , - , . . . . . . _ , . . . . ,
PLAN FOR ANALYSIS OF THE PROBLEM BILL JULIAN 08/17/91 QA0E File = HTX-XM1B Overall Concerns HAIN STEPUP TRANSFORMER FAULTED TO GROUND Short tera impact if not corrected:
NEED TO DETERMINE CAUSE AND TAKE PREVENTIVE ACTION PRIOR TO FLANT RESTART.
Longer ters impact if not corrected:
REPEAT FAILURE.
DEGRADATION OF PUBLIC, REGULATORY AND INVESTMENT CONFIDENCE Urgency of this concern:
TO ENSURE PUBLIC SAFETY TO COMPLY WITH THE CONF 00RMATORY ACTION LETTER TO RESTORE PUBLIC, REGULATORY AND INVESTMENT CONFIDENCE Deviation statement to work on now TRANSFORMER FAULTED TO GROUND Other people to involve in this analysis: q S. DOTY R. MAIN MAINTENANCE. T.XULCZYCKY SAFETY l l
Separate deviations involved:
TRANSFORMER FAULTED TO GROUND l
1
)
J
page 2 +
, - Plan for Analysis of the Problem Interia actions for : TRANSFORMER FAULTED TO GROUND DER #2-Q-91-???? INITIATED.
ROOT CAUSE IN-PROGRESS.
IDENTIFY APPROPROPRITATE PREVENTATIVE HEASURES.
- ENSURE PRESERVATION OF NECESSARY EVIDENCE FOR CAUSE DETERMINATION.
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2 PROBLEM SPECIFICATION 4
BILL JULIAN 88/17/91 ;
} QADE File 6 MTX-XM1B j i I 1
d Deviation Statement:
5 1
MAIN STEPUP TRANSFORMER FAULTED TO GROUND
! IS IS NOT i
l ._____ .....__...
! WNAT: OBJECT l l ...... _____
MAIN STEPUP TRANSFORMER 2MTX-XMiB 2MTX-XM1A ENERGIZED 4
2MTX-XM1C ENERGIZED ,
2MTX-XM1D SPARE <
WHAT: DEFECT j INTERNAL FAULT TO GROUND EXTERNAL-FAULT TO GROUND.
WHERE: GEDGRAPHIC UNIT 2 345KV SWITCHYARD UNIT 2 115KV YARD B MAIN TRANSFORMER ? OTHER UTILITIES ~
LOCATED SECOND FROM MOST WESTERY NOT UNIT 1 MAIN STEPUP TRANSFORM i
WHERE: ON OBJECT PRIMARY WINDING ? WINDING 70 HOUSING l WINDING TO CORE 1
i 1
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page 2 Probles Specification IS IS NOT WHEN: FIRST OBSERVED 13 SEPT 91 00548 ?CURRENTY OIL ANAYLSIS 2DOBLE TESTING I ?STARTUP TESTING
? PURCHASE TESTING WHEN: SINCE OBSERVED CONTINU0ULY SENCE EVENT ? PLOT OIL ANAYLSIS AND REVIEW
? REVIEW STARTUP DATA
? REVIEW TEMPERATURE PLOTS
? REVIEW WR HISTORY WHEN: LIFE CYCLE i ? LIFE EXPECTACY OF TRANSFFORMER ? DOBLE TESTING
? TIME IN SERVICE 7 DATA ANALYSIST
? ADDITIONAL TESTING / REVIEW /DATE l
EXTENT: HOW MANY 1 'B' MAIN TRANSFORMER (2MTX-XM1B) GREATER THAN 1 (A,C,D)
?HOW MANY OF LIKE TRANS FAILED /INUSE/?
EXTENT: WHAT PART
? PRIMARY WINDING ONLY. ? SECONDARY WINDING.
7 EXTENT ?HIGH OR LOW VOLT BUSHINGS
? OIL FAULURE
?INSULTATION EXTENT: PER UNIT l
l
? TO BE DETERMINED DURING ? TO BE DETERMINED.
DISASSEMBLY. (PU8RCHASE ORDER)
EXTENT: TREND
? UNKNOWN TUNXNOWN
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l DISTINCTIONS AND CHANGES BILL JULIAN 08/17/91 ,
QADE File = MTX-XM1B l
i Deviation Statement:
MAIN STEPUP TRANSFORMER FAULTED TO GROUND DISTINCTIONS CHANGES WHAT: OBJECT THE SPARE WAS NEVER PLACED -?WR'S l IN-SERVICE. -? MOD'S l -?S/U TEST DATA
-?
l WHAT: DEFECT
____.____... i
? APPEARS TO BE PRIMARY WINDING ? WINDING DELTA TEMP. VS LOAD I
? APPEARS TO BE WINDING TO CORE ? OIL DELTA TEMP. VS LOAD
?NOT VISIBLE FROM TOP ? ALARMS l ?NO COPPER SHOT VISIBLE FROM TOP l l
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WHERE: GEOGRAPHIC l l
WHERE: DN OBJECT
-PRIMARY CARRIES MORE CURRNET ????
.)
l page 2 I Distinctions and Changes DISTINCTIONS CHANGES 1
WHEN: FIRST OBSERVED SUNNER TIME WITH HIGHER AVE. TEMP.
WHEN: SINCE OBSERVED WHEN: LIFE CYCLE DISTINCTIONS WILL BE IDENTIFIED WHEN TEST DATA IS REVIEWED AND DEMOSTRATES REVELANT INFORMATION.
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Distinctions and Changes DISTINCTIONS CHANGES EXTENT: HOW MANY REVIEW OF PLANT OPERATING INFORMATION WILL DETERMIME DISTINCTIONS.
1 EXTENT: WHAT PART EXTENT: PER UNIT EXTENT: TREND I
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INFORMATION SOURCES BILL JULIAN 08/17/91 QADE File = MTX-XM1B j Deviation Statements ;
l MAIN STEPUP TRANSFORMER FAULTED TO GROUND WHAT: OBJECT Accuracy: HIGH DER 2-9-91-????, OIL ANAYLIS (E:A),
WHAT: DEFECT Accuracy: HIGH DER #2-91-0-????, OIL ANALYSIS, VISUAL INSPECTION 8/16/91
^" ""*" '"
i ""*".?"??"*""'?
ALARM PRINTOUT FROM POWER CONTROL, OSCILLISCOPE PRINT FROM SCRIBA YARD l
l l
WHERE: ON OBJECT Accuracy: LOW OPION OF H. LIGHT BASED ON VISUAL ONLY.
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WHEN: FIRST OBSERVED Accuracy: LOW OIL ANALYLIS TO BE PLOTTED AND REVIEWED.
REVIEW OF OTHER DATA.
WHEN: SINCE OBSERVED Accuracy: LOW EPM-Q2/ EPM-GEN-0692, EPM-GEN-D99699, WTS, WHEN: LIFE CYCLE Accuracy: LOW
?EPRI, INDUSTRY EXPERIENCE REVIEW, COMPARE OF l OTHER MAIN TRANS DATA, OTHER.
Page 2 ,
Information Sources EXTENT: HOW NANY Accuracy: LOW TOUESTION NETWORK FOR LIKE TRANS.
EXTENT: VHAT PART Accuracy: LOW VISUAL INSPECT., H. LIGHT, DIL ANAL.,
EXTENT: PER UNIT Accuracy: LOW l
l EPRI, REBUILD VENDOR, INDUSTRY EVENTS.
i EXTENT: TREND Accuracy: LOW NETWORK, EPRI, i
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LIST OF POSSIBLE CAUSES ;
BILL JULIAN 08/17/91 I
QA0E File = HTX-XM18 j Cause Status DIELECTRIC FAILURE NOT TESTED :
l INSG ATION FAILURE NOT TESTED !
NECHNICAL FAILURE NOT TESTED l ENF FAILURE NOT TESTED I MANUFACTORING/ INSTALLATION /ASSEMPLY DEFECT NOT TESTED i l \
ELECTROSTATIC NOT TESTED l
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4 NRC - INTERFACE
- The following material and information have been provided to the NRC
i 1. Daily 345KV yard recovery maintenance schedule.
l l 2. a) Transformer oil testing values prior to the transformer failure, b) Transformer oil testing values subsequent to the transformer failure.-
{ 3. a) Phase B transformer oil dielectric testing value prior to the transformer i failure.
l l b) Phase B transformer oil dielectric .' testing values . subsequent to the l transformer failure.
- 4. McGraw Edison Main Transformer Instruction Book.
! 5. A computer print out of maintenance perfomed on the main transformer.
l l 6. The initail installation test results.
- 7. Daily Electrical Department 345KV switchyard readings.
- 8. Operator Rounds Guide.
- 9. Copy of the latest completed outdoor transformer Preventative Maintenance l Procedure.
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MAIN TRANSFORMER READINESS FOR RESTART The gas in oil analysis for the main step up transformers has been reviewed to determine if problems exist within the transformers. There are several methods used to make these determinations and the conclusions will be included in this report. Although there is expertise within Niagara Mohawk, various utilities, vendors (including McGraw Edison) and personnel have been consulted to verify the conclusions. These results were analyzed to determine if this failure could have been predicted, the readiness to restart the other main transformers and finally what precautions should be taken to monitor the transformers once they are reenergized.
The qualitative interpretation of certain gases can indicate trends or potential problems.
The magnitude of the gases in the stepup transformers do not indicate any immediate concern but will be monitored daily until such time generation personnel are convinced no problems exist.
Other methods ofinterpretation include the Rogers and Dornenberg rate method. These methods indicate some local overheating but again the consensus is that no further actions need to be taken other than close monitoring. McGraw Edison has reviewed the data, agreed with the conclusions and recommends close monitoring. This local overheating can cause insulation problems, but Doble testing, including power factor tests as recommended by Harold Moore, (EPRI recommended) were satisfactory.
This data was also reviewed by Joe Kelly (SD Myers Co., also a member of the IEEE Committee on Dissolved - Gas Analysis). The transformers have been backfed for 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br /> without load as recommended by Mr. Kelly and Mr. Harold Light and no increase in gases was seen. Mr. Kelly indicated increased surveillance after energizing.
The moisture content of the transformers was close to the acceptance criteria. An independent lab performed the same tests and the results were better than those performed by Niagara Mohawk. McGraw Edison was contacted and suggested a different sampling procedure.
After resampling, the results were well within the acceptance criteria.
Daily oil samples will be taken to monitor gas trends. Total ppm combustible gas will be closely monitored and a decision will be made at the time a significant increase is noticed. In !
addition to the gas samples daily dielectric and water in oil tests will be performed. The same trending will be conducted by the Site, the Safety Analysis Group at Salina Meadows and by a j Senior Engineer in the System Equipment Analysis Organization. Consultants will be contacted ,
as the need arises. The frequency will be revised if no adverse trends are noted and when the i
disciplines involved concur, i All the latest data has been compiled in the attached charts. The individual gases and the i acceptance criteria are shown. Any gas that exceeds the limit is noted and an explanation given. l The supporting documentation for these conclusions as listed is attached, l
- 1) Letter from Harold Light, Niagara Mohawk Senior Engineering Specialist.
- 2) Memo from Bernie Bernales, Niagara Mohawk Engineer, Safety Analysis Group.
- 3) Memo from Paul Ahrens, Wisconsin Electric Power Company.
- 4) Notes of telecon with Joe Kelly, S.D. Myers.
- 5) Telecopy from Harold Moore, retired from Westinghouse, recommended by EPRI.
In conclusion, all the Niagara Mohawk personnel that reviewed the data and those consulted agree the transformers can be energized with no additional corrective or preventative actions. Close monitoring (daily) and trending will determine if additional corrective actions will need to be taken. Should any problems. occur, degassing of the main step up transformers will need to be performed.
j
TRANSFORMER MTX-XMIA DISSOLVED GAS ANALYSIS ECOMPONENT PPMJ LIMIT * ^ ?6/21/91 ; 8/14/91i 8/23/91i 18/27/917 $8/28/91; 18/2$/90 8/30/9ij 113 -Ilydrogen 100 17 24 18 17 14 18 23 0 2- Oxygen 3087 3515 3310 1129 655 1125 7193 Cil. - Methane 120 63 92 68 57 69 70 72 CO - Carbon Monoxide 350 267 421* 292 252 286 285 366*
CO, - Carbon Dioxide 2500 5163* 8983
- 5843
- 4989* 5788* 6224* 6152*
Call. - Ethylene 50 0 0 0 55 2 0
C 311. - Ethane 65 53 68' 52 72 8 53 56 50 C2ll, - Acetylene 35 0 0 0 15 2 0 0 0
% Total Gas 6.17 6.86 6.05 4.13 4.11 4.60 8.98 Totd Combustible Gas - PPM 720 401 605 430 467 421 428 475 iCOMPONENT PPM $ LLIMITl D/1/90! d2/21/91l i8/14/9b l$3/sif ' (9/4/911 1I2 0 20 9 15 38 8 20 12 These limits are taken from the draft revision of IEEE C57.104, " Guide for the Interpretation of Gases Generated in Oil-Immersed Transformers", Draft 12. This is generally referred to as the " Gas Guide". This document was selected over the currently approved version due to this version being more conservative and the approved version lacks clarity. This version was approved by the subcommittee and is in the process of being approved by the whole transformer committee, as well as being used by the industry experts contacted for this concern.
Note: During the course of this evaluation numerous experts in the industry have provided assistance and assessments of the dissolved gas analysis. The following is a list of people utilized to provide assessments of this dissolved gas analysis data: liarold Light, Niagara Mohawk Power Corporation; Joe Kelly, S. D. Myers Transformer Consultants; liarold Moore.
Westinghouse retired, recommended by EPRI; Paul Ahrens. Wisconsin Electric Power Company,21 years experience with these type transformers.
8 This data was evaluated by industry experts and found to be higher than the limit but in-line with expected results subsequent to a fault.
These occurrences were attributed to an anomaly in the analysis lab, as a result the initial samples will be verified by an independent lab through duel samples.
This high II 02 was attribute <* to sample technique which has been modified.
All experts identified the higher than expected CO/CO2 concentrations indicative of localized overheating. but only recommended monitoring in accordance with IEEE. This data was also reviewed by the transformer expert at Wisconsin Electric Power Company. They indicated that this CO/CO 2 generation is similar to operational performance they have experienc with these type of transformers and concurred also with our intent to energize this transformer.
TRANSFORMER MTX-XMIC I DISSOLVED GAS ANALYSIS
?COldPOAENT PPM @ ! LIMIT
- 15/29/911 J6/18/91_ 8/14/917 8/23/91- 8/28/91- 8/29/91' 8/30/91[ ,-
t II, - liydrogen 100 10 1 56 20 14 16 19 O, - Oxygen 2288 52II 1517 4308 5774 3073 2057 CII. - Methane 120 126' 111 155' 148' 129 ' i18 1338 8
CO - Carbon Monoxide 350 350 369 450 8 407 8 318 200 40I 8 CO, - Carbon Dioxide 2500 4183 8 4409 8 8474 8 6875 8 5635 , 5797 8 6398 8 C,II. - Ethylene 50 33 31 0 0 38 0 0 C,H. - Ethane 65 177' 161 8
204' 2M ' 214' 160 ' 175' C,II,'- Acetylene 35 0 0 0 0 0 0 0
% Total Gas 8.64 9.44 8.93 9.98 8.33 7.51 7.84 Total Combustible Gas - PPM 720 697 674 866 779 713 495 728 ICOMPONENTIPpMS LLIMITT f2/21/911 18/14/911 ?9/3/91< 19/4/91 ~
1 8
11, 0 20 17 52 15 9
- These limits are taken from the draft revision of IEEE C57.104, " Guide for the Interpretation of Gases Generated in Oil-Immersed Transformers", Draft 12. This is generally referred to as the " Gas Guide
- This document was selected over the currently approved version due to this version being more conservative and the approved version lacks clarity. This version was approved by the subcommittee and is in the process of being approved by the whole transformer committee, as well as being used by the industry experts contacted for this concern.
Note: During the course of this evaluation numerous experts in the industry have provided assistance and assessments of the dissolved gas analysis. The following is a list of people utilized to provide assessments of this dissolved gas analysis data: llarold Light, Niagara Mohawk Power Corporation; Joe Kelly, S. D. Myers Transforuer Consultants; liarold Moore, Westinghouse retired, recommended by EPRl; Paul Ahrens, Wisconsin Electric Power Company,21 years experience with these type transformers.
This data was evaluated by industry experts all of which concurred with our expert in that there is no reason not to energize these transformers. Gassing of this transformer was evaluated and attributed to unique characteristics which would not preclude satisfactory operation. The recommendation is to observe trend of these hydro carbons for significant increases in gas content.
8 All experts identified the higher than expected CO/CO, concentrations indicative of localized overheating, but only recommended monitoring in accordance with IEEE. This data was also reviewed by the transformer expert at Wisconsin Electric Power Company. They indicated that this CO/CO, generation is similar to operational performance they have experienced with these type of transformers and concurred also with our intent to energize this transformer.
8 This high II,O was attributed to sample technique which has been modified.
TRANSFORMER MTX-XMID DISSOLVED GAS ANALYSIS TCOMPONENT PPMc T LIMITT L2/21/91: 55/29/911 08/14/913 !8/23/91) 1 8/28/919 18/29/90 48/30/911 II,-Ilydrogen 100 16 10 22 8 7 8 14 O2 - Oxygen 399 10667 1904 1066 1657 I819 1104 CII. - Methane 120 36 37 46 37 46 47 49 CO - Carbon Monoxide 350 99 82 124 103 114 92 135 CO2 - Carbon Dioxide 2500 274 296 360 281 432 462 482 C2 fl. - Ethylene 50 9 Ii 10 8 10 1I 11 C 211. - Ethane 65 87' 91' 102' 81' 102' 108' 108' C,II, - Acetylene 35 0 0 0 0 0 0 0
% Total Gas 4.82 10.01 6.32 5.26 5.73 6.04 5.83 Total Combustible Gas - PPM 720 248 232 304 238 280 265 317
- lCOMPONENT PPM [ TOMIT- ;5/3/903 02/21/91s 18/14/96 (9/3/911 f9/4/91: .
1I2 0 20 11 15 50 8 228 11 5
These limits are taken from the draft revision of IEEE C57.104, " Guide for the Interpretation of Gases Generated in Oil. Immersed Transformers", Draft 12. This is generally referred to as the " Gas Guide". This document was selected over the currently approved version due to this version being rnore conservative and the approved version lacks clarity. This version was approved by the subcommittee and is in the process of being approved by the whole transformer committee, as well as being used by the industry experts contacted for this concern.
Note: During the course of this evaluation numerous experts in the industry have provided assistance and assessments of the dissolved gas analysis. "Ihe following is a list of people i utilized to provide assessments of this dissolved gas analysis data: liarold Light, Niagara Mohawk Power Corporation; Joe Kelly, S. D. Myers Transformer Consultants; liarold Moore, ,
Westinghouse retired, recommended by EPRI; Paul Ahrens, Wisconsin Electric Power Company,21 years experience with these type transformers.
This data was evaluated by industry experts and appears too' e due to natural aging of the oil, 2
This higher than expected II2 0 was attributed to sampling technique which has been modified.
l INTERNAL CDRRESPONDENCE comun=== ss e .ots MV Ny Facu HF Light Distnici System Equipment Analysis To S Doty DATE September 3,1991 FILE CODE SUBJECT Retum to Service of Phases A, C & D of the GSU Transformer for !
Nine Mile #2 !
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l Over the last three weeks I have reviewed the physical and chemical properties of the oil within Phases A, C and D.
I have reviewed the electrical tests that have been perfonned after the August 13th failure of Phase B. I concur with the soaking of the units from the high side prior to energization from the generator. Gas in oil analysis will be performed after the unit is energized from the generator. I agree with the~ sampling procedure agreed upon prior to and after the units are energized. The units will be closely watched due to the slight presence of some gases.
I do not find any variances in any of the data to date that would not prevent the energization of these transformen.
IRF Light //
Senior Engineering Specialist Equipment Analysis HFL/jde xc: WE Adams Jr i
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l 91 FFI 15:31 BC FM 10. 4142212318 P.02-l August 30, 1991 To: Bill Julian Niagara Mohawk Power Company Re: The Dissolved Gas Analysis Graphs Forwarded on 8/29/91
- 1. The dissolved gas analyses (DGA's) for the transformer that failed (2b) provided no indication that there was a problem. Therefore, it seems appropriate to assume that the problem was a relatively fast evolving one.
- 2. The dissolved gas analysis results forwarded to me revealed nothing particularly alarming. The CO, levels in the 2a and 2c transformers are a little higher than desirable but not alarmingly so. If the CO: levels exceed 10000 ppm and continue to increase it would be a good idea to de-gas the oil during the next refueling outage.
- 3. The high CO, levels are usually indicative of cellulose insulation operating at temperatures between 120 and 140 degrees C. This is usually considered warmer than desirable for normal operation of transformers but acceptable during emergency conditions. Frequently the cause of the high temperatures is less than optimally clean coolers or restriction of air flow to the coolers. Cleaning the coolers using low pressure steam, preferably directed from the back of the coolers (direction opposite that of the normal air flow), can be effective. Care must be taken with some i
' coolers not to damage the thin plate fins with steam that is applied at a pressure that is too high. Another cause for the high CO, levels could be fans that are not operational. Installations of fans with greater air flow can enhance cooling. However, the greater air flow fans can also result in more fouling of coolers.
- 4. The transformers can be made to run cooler by keeping all of the cooling equipment operational whenever the transformers are loaded rather than allowing the cooling equipment to cycle based on top oil or hottest spot temperatures. However, care must be exercised with lightly loaded EHV transformers not to create a situation conducive to static electrification.
i It would be best to consult the manufacturer before making all cooling equipment operational on any lightly loaded EHV transformer.
- 5. The information forwarded to me did not include information regarding the water content of the oil in the subject transformers. It is a good idea to watch the H2 O content of the oil in EHV transformers. If the water level exceeds 10 ppm the transformer warrants closer monitoring. If it exceeds 15 ppm, the transformer should be dried out. Consult the manufacturer for recommendations.
The above suggestions and opinions are provided by Wisconsin Electric Power company as an accommodation to Niagara Mohawk Power Company. Wisconsin Electric Power Company assumes no responsibility for the accuracy or suitability of the information and Niagara Mohawk Power Company understands that it uses this information at its own risk.
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l AMALYSIS OF DATA ON NIAGARA MOHAVX GENERATOR TRANSFORMKR '
The fot r+41ng analysis is based on a rather short study of the p n in oilandtjtherdata supplied to me by Niagara Mohawk. The opinid.n
- formed nva based on this limited information. More time and stdt the coq >'ete operating history of these transformers would be Id,y of uired f or a g' v.4 analysis.
Therefore, it must be recognized that the!;
opinionq' expressed in this document are not based on complete j '
infornation and therefore may have limited value so that I cann@.
r accept rispensibility for problems that may arise from .these '
transf c.r .e r s. !
1 4
A ANALYS!S OF DATA SUPPLIED j The gar in oil data supplied indicates that there is a thernal [ chlem l
in them.i' of quanitih:j transformers carbon dioxide which is overheating cellulose insulation.{
[CO2)
The 4 and carbon monoxide (CO3 are rpeve i nornal.., Depending on the interpretation method used, the severi'y of the pro'.b2m varies from " greater than normal" to "a high level rlC decomp.'h!. tion which should prompt additional investigation". A V1, three p{ the transformers in the bank when the failure occurree had sistler .3assing patterns. The quanities and- ration are considnt e.bly above wh q t I would consider normal for transformers produced id I.he
- 198 0' e . . ,Vh i le there are other transformers in service with th.p n valuer..< ihe continued upward trend in the CO and CO2 are an ind vation j
4 that a '. ,otinuing problem exists.
The hy(-dgen is rather nominal indicating that there is no sert" uh phrtisi jischarge problem. There is no detactable upward trend in the hy.L ?gan.
l The ot h q hydrocarbons do not indicate any serious trends with the l exceptika of the ethane (C2H61 in unit 2C which has been increm tr.3 since 1Qi?. The methane in this unit is also higher than the o bsr
, units. Ibis gassing trends on this transformer should be obser ed !
since tV.#re is this upward trend in the hydrocarbons. 1
! There isijc,reased oxygen a commoninoccurrance in all all three near thethree end transformes in that of 1990 or early ty>?
199%
4 Tba records 'phould be checked to determine if the transformers or whethejr there has been any. problems with the oil preservatinr were byened i
system.
The watit in oil content of 26 ppa reported for unit 2B is on t?i.s high side fde',a 345 kv transformer with the rubber bag type of oil l preser(s j ien. The other units should be checked to determine th itr water dar. tent. If they are in this order of magnitude, you may want tocon(iferwhethertheyshouldbeenergizedwiththesewaterId .al e.
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i I did r,?.C, find anything in the gas in oil data that would prevor.,'.
putting'itese transformers into service. However. it must agair.' be realized t. hat this is based on limitei information and time to s Jdy the protdam. There are situations that are causing the CO and dQ to incread in all units and for the methane and ethane to increa?./ n 2C j which th:Yild be of concern. The sources of gas may not be saribu(s enough } j c.ause problems, but caution is recommended until the fhlled transfotver has been dismantled for inspection.
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! Prior to energizing the transformers, I recommend a complete et 4..f t oil ter.1 i and power factor tests on the transformer insulation th' insure Oht all three units are in good condition. If any quan[;. ics are nc,t rNtisfactory, energization is not recommended. The oil 4 should d r:cl ude carefully conducted water in oil and VDE dielect<f'r.rota tests 7 i
i The ea re f a for the increases in oxygen should also be investiga r.-d since 't hic may be an indication of a leak or other problema.
, Pleane ndte that the ethane has continued to increase in the id'..a t r a n sf c.: br .
If all of the tests are satisfactory, and it in decided to put tM l
units th ,k on the line; caution is recommended and the transft.s, .or e
, should ta observed frequently for several days.
l If I ca Y be of further assistance, please notify me.
1 Sincerely, H rold R.
Fh<we ;
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a Rev. 1 1 ROOT CAUSE REPORT FOR THE EXIDE UPS 1A, B, C, D, G TRIP EVENT OF AUGUST 13,1991 SEPTEMBER 9,1991 FILE CODE: NMP77748
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John Co y JoM Q weesh' oot Cause ator Root Cause Facilatator Tech. Support ISEG Engineer l
I Reviewed By:
w A0
! pesR.Director,dpacfafore Pr(ogram i
! ISEG I
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t PURPOSE / SCOPE This report has been generated to document the analysis of the root cause for the tripping of Uninterruptable Power Supplies (UPS) 2VBB-UPS 1A, B, C, D and G and the failure to transfer their loads to the maintenance supply.
This analysis was performed in accordance with NDP-16.01 by reviewing plant operator and damage control team observations and actions, performance of troubleshooting activities on in-plant equipment, review of various drawings, performance of laboratory diagnostic testing, consultation with the UPS manufacturer, review of data recorded during the event, and consultation with other industry experts.
ABSTRACT On August 13,1991 at 5:48 AM an electrical fault on the B phase main step-up transformer occurred. At that same time five (5) Exide Uninterruptable Power Supplies (UPS) tripped simultaneously. Transfer of the UPS's loads to the maintenance power supplies did not occur. The system conditions as documented by operators that were dispatched to restore the units immediately after the incident as well as observations by the System Engineer and other damage control team members indicated that the UPS's logic had tripped their input and output breakers. Post event review of equipment drawings with the vendor revealed that the DC power supply which powers the system control logic normally draws its power from the maintenance power supply. The inverter output is utilized as a backup source. This scheme of connection allows transients on the AC power line to be transmitted to the DC logic power supply. Tests performed by the System Engineer support this conclusion. The bypass breaker CB-4 did not close and transfer the UPS loads to the maintenance supply. This functioned per design since permissives for CB-4 closure were not satisfied due to the degraded voltage conditions present ;
on the maintenance supply.
The initial inspection of the units revealed that alarm indications on the five units were not identical. The inverter logic alarm light was not lit on UPSIG but was lit on A, B, and C.
The voltage difference alarm indication did not clear on 2 out of 5 units (Alarm should clear in )
10-15 seconds after condition clears). The over-voltage /undervoltage (OV/UV) alarm was ;
present on 3 out of 5 units although all units should have displayed this alarm. In addition, none of the 10 LEDs that indicate the initiating signals for a logic trip were lit on any of the UPS units.
i l
I Page 1 i
t
- DISCUSSION On August 13,1991 at 5:48 AM a ground fault occurred on the B phase main transformer. This event was detected and recorded on the Scriba Substation oscillograph. Five Exide UPSs (2VBD-UPS 1A,B,C,D, and G) tripped during this event resulting in a loss of power to all their loads.
The results of observations by plant operators and damage control team personnel are summarized on Attachment 1. All five UPS loads were initially restored to their maintenance supplies by plant operators after initially attempting (unsuccessfully) to restart the D unit. The damage control team was able to restart the C, D, and G units. The A and B units were left on the maintenance supply because the damage control team was not successful in restarting those units.
As a result of these observations, it has been concluded that all five units shut down as a result of a logic initiated trip. This conclusion is based on the as found positions of breakers CB-1,2,3 on all five units and the presence of the module trip alarm on all the units except D which was reset by a plant operator while attempting to restart that unit. It is noted however, that none of the 10 LEDs on the A13A21 card which should indicate what condition caused the logic to trip were lit. In addition, two units (UPSID, UPSIG) displayed voltage difference l alarms. This alarm indication should have cleared in 10-15 seconds after the plant operators !
manually restored the UPS loads to the maintenance supply. The OV/UV alarm indication was present on three units only, (UPSIC, UPSID, UPSIG), although all units would be expected to display that alarm indication. The inverter logic alarm light was not lit on UPS1G although it was lit on the other units that were not initially reset (UPSI A, IB, and IC).
Breaker CB-4 was found open on all five units. A review of the oscillograph recording indicates that for the duration of the transformer fault (i.e., approx.100 msec.) the B phase voltage of the station's normal AC distribution system decreased to approximately 50% of its normal level. It has been concluded that this condition prevented the automatic transfer of the UPS's loads to their maintenance supplies. This is due to a logic feature which prevents static switch transfer to the maintenance supply under conditions that could cause damage to the connected loads.
The following potential causes for the simultaneous tripping of the five UPSs were evaluated:
(1) Voltage transient on the B phase of the normal AC distribution system (2) Propagation of high frequency noise from the main transformer fault (3) Voltage transient on the station ground system Page 2
i 6
Transmission of high frequency noise from the transformer fault through the atmosphere to the UPS units could not have caused the UPS trips. Preoperational testing demonstrated that the units are not sensitive to radio frequency (RF) transmissions unless the panel doors are open and an RF source is in close proximity. The report provided as Attachment 2 indicates that it is unlikely that high frequency noise could have been transmitted through the station's normal AC distribution system to the UPSs due to intervening transformers that would filter such a signal. As a result, potential cause (2) is not considered credible.
Potential Cause (3) is considered unlikely due to the fact that one of the five UPSs is located in an area substantially away from the other four units yet exhibited similar behavior.
In addition, no other station equipment (including other UPSs) appears to have been affected by a ground transient. Initiallaboratory testing indicates that a significant ground transient would have caused the destruction of numerous logic circuit components which has not been observed in the field. Further laboratory tests are being conducted in an attempt to identify the mechanism by which inconsistent alarm light indications were received. Potential Cause (1) was investigated as the most probable cause.
Troubleshooting performed following the event to evaluate and demonstrate the validity of potential cause (1) indicated the following:
- 1) The DC logic power supply for UPSs l A, B, C, D, G is normally fed from the B phase of the maintenance supply with the inverter output supply as a backup.
l
- 2) The trip point of the DC logic is at 17.3 VDC for UPSID corresponding to 84.5 l
VAC on its input; and 16.9 VDC for UPSIC corresponding to 84.59 VAC on its input.* New control batteries (fully charged) only provide approximately 18 VDC.
- 3) Transfer to alternate power is accomplished via a K-5 relay. K-5 relay drop out l
voltage is 45 VAC for UPSIC and pick up voltage is 52 VAC.
l K-5 relay drop out voltage is 42 VAC for UPSID and pick up voltage is 55 l VAC.
- I
- 4) Voltage transients generated during troubleshooting on the normal AC input power line feeding UPSIC did not trip the UPS.
- These measurements were not repeated on the other units since the results were essentially the :
same for the C and D units and should not be any different for the A, B, and G units. '
l i
l Page 3 )
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i.
i
- 5) The internal logic batteries on all five units were in a degraded condition and were not capable of sustaining proper logic voltage when all other sources were
! disconnected. There is no way to determine that the batteries are in a degraded condition with the current UPS design during normal operation.
- 6) Voltage transients injected (i.e., dropping AC input voltage to near zero for 100-200 msec.) on the maintenance power line in combination with the degraded batteries affected the DC logic such that it tripped the units without allowing the l
K-5 relay to change state. This was demonstrated on UPSIC and UPSID.
i
- 7) A sudden complete loss of the maintenance supply voltage with both new and degraded batteries installed did nel cause the unit to trip. In this case, the logic
. power supply properly transferred to the inverter output and therefore prevented j a trip.
- 8) Voltage transients injected on the maintenance power line (i.e., similar to those utilized in 6) above) with good batteries installed did not produce any unit trips, although some voltage perturbations on the logic power supply were observed.
l This was demonstrated on UPSIC and UPSID.
- 9) Fully charged batteries are required for successful K-5 relay transfer under some degraded voltage conditions on the maintenance line since other-wise the unit may trip on logic power supply failure < 16.9 VDC (84.5 VAC) before the K-5 relay will transfer the logic power supply to the inverter output.
Laboratory testing is being conducted to more fully evaluate the condition of critical components and to investigate why none of the 10 LEDs were lit on the A13A21 board even though the logic was tripped. The pertinent results of this testing to date indicate the following:
- 1) Significant ground voltage transients' applied to certain circuit components causes their destruction.
- 2) Injection of noise into the boards has not caused a trip signal to be generated.
Laboratory testing will continue to further investigate the inconsistent alarm light indications. The outcome of this work is not expected to affect this root cause determination or the functionality of the UPSs. Results ofin-plant troubleshooting and laboratory testing to date indicate proper function of the various alarms.
Page 4
o A review of the UPS vendor manual resulted in the identification of the following deficiencies:
l The vendor manual implies that the function of the batteries is to allow logic l
testing with no other input power available to the logic. This contributed to the system engineer not knowing that fully charged batteries could prevent a trip.
The following statement is from the vendor manual:
"A redundant logic supply, powered by the inverter output, a separate 120 VAC bypass source, and/or internal rechargeable sealed batteries, allows logic testing with no input power applied and keeps alarms indicating for as long as any source of AC control power is available."
l The section of the vendor manual which describes preventive maintenance does not mention the logic batteries, In addition, the general description section of the manual states, i
"(The batteries should be replaced at 4-year intervals)".
The 4-year replacement frequency is not satisfactory for service over the acceptable ambient temperature range specified for the UPSs.
The description of the logic power supply in the manual (shown below) is incorrect.
"These power supplies are powered through relay A27K1, which selects inverter output (preferred) or bypass (alternate) source."
As a result of discussions with the UPS vendor it has been determined that the logic backup batteries are not designed to mitigate a degraded voltage condition. Additionally, the UPS design does not provide a battery test feature or allow for safe replacement of the batteries without removing the entire unit from service. Removing the unit from service would result in de-energizing the connected loads.
CONCLUSIONS
- 1) The main transformer fault caused a voltage drop on the maintenance supply to all five UPS units.
- 2) The degraded voltage on the maintenance supply caused the voltage on the UPS logic power supply to decrease below its trip setpoint causing the units to trip.
Page 5
0 4
- 3) Automatic load transfer to the maintenance supply was prevented by design due to the degraded voltage conditions on the maintenance supply.
- 4) The root cau.se for the simultaneous tripping of the UPSs is improper design. The UPS is not designed to accomodate a degraded voltage condition.
The following design deficiencies allowed the UPS logic power supply voltage to decrease below its trip setpoint as a result of the main step up transformer fault.
The logic power supply is normally energized from the maintenance supply with the inverter output as a backup instead of visa versa.
Under degraded voltage conditions the logic power supply switching circuit does not actuate until the supply voltage has decreased to well below the level that will cause the logic to trip.
- 5) Fully charged batteries probably would have prevented the tripping of the UPSs even though that is not part of their design.
CORRECTIVE ACTIONS
- 1) Modify the UPS logic power supply for units 1A,B,C,D, and G to be inverter preferred with maintenance backup prior to plant restart.
- 2) Replace all UPS logic backup batteries prior to restart.
- 3) Prior to restart review other plant hardware which utilizes backup batteries and verify that appropriate replacement schedules exist for those applications. Ensure any control functions dependent on batteries are identified prior to restart.
- 4) Process appropriate changes to the UPS vendor manual to address the identified deficiencies.
RECOMMENDATIONS 1
- 1) Evaluate (post restart) further logic power supply modifications to rectify the K-5 !
relay drop out characteristic problem and to provide easy access to the logic batteries for testing and replacement.
- 2) Develop an appropriate replacement schedule for the logic batteries based on supplier recommendations, actual service conditions, and purpose of batteries.
Page 6
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ATI'ACHMENT 1 Page 1 of 5 8/13/91. UPS FAILURE TO TRANSFER ON TRANSIENT ON AC INPUT:
A.) Operators responded to 2VBB-UPSI A,1B,1C, ID, IG and found the following: .,
1.) UPSI A: a.) CB-1 tripped ,
b.) CB-2 tripped c.) CB-3 OPEN d.) CB-4 OPEN ,
e.) . - AUTO restart f.) CB-3 switch closed g.) Module TRIP h.) Inverter Imgic Alarm l 2.) UPSlB: a.) CB-1 tripped b.) CB-2 tripped ,
c.) CB-3 OPEN d.) CB-4 OPEN e.) AUTO restart f.) CB-3 switch closed '
g.) Module TRIP h.) Inverter Logic Alarm 3.) UPSIC: a.) CB-1 tripped b.) CB-2 tripped c.) CB-3 OPEN d.) CB-4 OPEN e.) AUTO restart f.) CB-3 switch closed g.) Module TRIP h.) Inverter Logic Alarm i.) OV/UV 4.) UPSID: a.) CB-1 tripped b.) CB-2 tripped c.) CB-3 OPEN d.) CB-4 OPEN e.) AUTO restart f.) CB-3 switch closed g.) No module TRIP h.) No Logic TRIP i.) OV/UV j.) OV/UV Transfer.
k.) Voltage Difference Page 7
h l
I^
ATTACIIMENT 1 Page 2 of 5 5.) UPSIG: a.) CB-1 tripped b.) CB-2 tripped c.) CB-3 OPEN i d.) CB-4 OPEN e.) AUTO restart f.) CB-3 switch closed l g.) Module TRIP h.) Voltage Difference i.) OV/UV l
B.) The operators did the following manipulations in attempting to restore the UPS':
1.) UPSI A:
I !
l a.) Placed restart switch to MANUAL b.) Placed the CB-3 toggle switch to OPEN position.
l c.) Reset the alarms d.) LIFTED CB-4 MOTOR OPERATOR AND MANUALLY CLOSED 1 CB-4. = see note 1
2.) UPSlB:
l a.) Closed CB-1 b.) Closed CB-2 c.) Reset the alarms d.) LIFTED CB-4 MOTOR OPERATOR AND MANUALLY CLOSED CB-4.
- see note 3.) UPS1C:
a.) Placed restart switch to MANUAL b.) Placed CB-3 toggle switch to OPEN position c.) LIFTED CB-4 MOTOR OPERATOR AND MANUALLY CLOSED CB-4.
- see note 4.) UPS1D:
a.) Closed CB-1 b.) Closed CB-2 c.) Reset the alarms d.) LIFTED CB-4 MOTOR OPERATOR AND MANUALLY CLOSED CB-4.
- see note.
Page 8
4
~
ATTACIIMENT I Page 3 of 5 5.) UPS1G:
a.) Placed CB-3 toggle switch to OPEN position.
b.) LIFTED CB-4 MOTOR OPERATOR AND MANUALLY CLOSED CB-4.
- see note
- NOTE: When the operators tried to restart UPSID the procedure called out verifying that CB-4 was closed but it was open. The operators l made a decision to energize the UPS loads by manually closing i CB-4 by first lifting the motor operator off of the breaker. They l restored each UPS in that same manner.
l l C.) At approximately 0830 the system engineer went down with damage control team #3 l (operators, electricians and I/C technician) to restore each UPS.
UPSIC: Found CB-1, CB-2 tripped and CB-3 was open. CB-4 was closed and the CB-4 motor operator (in the OFF position) was lifted off breaker.
Removed P6 plug from the CB-4 motor operator and aligned the motor operator to the ON position. Reset all alarms. Closed CB-1 and restarted the unit. It started up and " synced" to the maintenance supply. Closed CB-2, restored P6 plug and reinstalled the motor operator for CB-4 back on the breaker. Transferred the load to UPS power and put transfer switch in AUTO position.
UPSID: Found CB-1, CB-2 closed and CB-3 was open. CB-4 was closed and the CB-4 motor operator (in OFF position) was lifted off the breaker.
Removed P6 plug from the CB-4 motor operator and aligned the motor operator to the ON position. Opened CB-1 and CB-2. Closed CB-1 and restarted the unit. It started up and " synced" to the maintenance supply.
Closed CB-2, restored P6 plug and reinstalled motor operator for CB-4 i back on breaker. Attempted to transfer load to UPS power but CB-3 would not close. It was found in tripped position. CB-3 was reset, the motor operator was restored and the unit transferred to UPS power. Put the transfer switch in AUTO position.
Page 9
ATTACIIMENT 1 Page 4 of 5 UPSIA: Found CB-1 and CB-2 tripped and CB-3 was open. CB-4 was closed and the CB-4 motor operator (in OFF position) was lifted off the breaker.
Removed the P6 plug from the CB-4 motor operator and aligned the motor operator to the ON position. Closed CB-1 and attempted to restart the unit. Closing CB-1 caused an inrush to the UPS and tripped the upstream breaker, 2VBB-PNL301, breaker #1. Reset breaker in 2VBB-PNL301 and reclosed CB-1 on UPSI A. Upstream breaker tripped again.
Wrote WR (WR # 162319) and Deficiency tag to repair Rectifier section of UPSIA. Unit left with CB-4 closed.
UPSlB: Found CB-1, CB-2 closed and CB-3 open. CB-4 was closed and the CB-4 motor operator (in OFF position) was lifted off breaker. Removed P6 plug from the motor operator and aligned motor operator to ON position.
Opened CB-1 and CB-2. Closed CB-1 and restarted unit. It started up and " synced" to the maintenance supply. Closed CB-2, restored P6 plug and reinstalled motor operator for CB-4 back on breaker. Attempted to transfer load to UPS power but CB-3 would not close. It was found in the tripped position. CB-3 was reset, the motor operator was restored and attempted to transfer load to UPS power but CB-3 again would not close.
CB-3 cannot be reset due to a previously identified problem. Unit left with CB-4 closed - on Maintenance supply power.
Note: WR# 138173 exists to replace CB-3.
Page 10
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ATTACHMENT 1 Page 5 of 5 !
l UPSIG: Found CB-1, CB-2 tripped and CB-3 open. CB-4 was closed and the CB-4 motor operator (in OFF position) was lifted off breaker. Removed P6 plug from motor operator and aligned motor operator to ON position.
Reset all alarms. Noted 575vac input to UPS. Closed CB-1. When CB-1 was closed it tripped its upstream breaker in 2VBB-PNL301. Breaker #7 in 2VBB-PNL301 was reset and CB-1 reclosed (successfully). The unit was restarted. It started up and " synced" to the maintenance supply.
I Closed CB-2, restored P6 plug. When restoring the P6 block the CB-4 l motor operator went to the OFF position. Opened CB-2 and CB-1 and i removed logic power from unit to reset all logic. Reset motor operator l on CB-4 to ON position. Reclosed logic power, closed CB-1 and restarted UPS. Unit started up and " synced" to the maintenance supply.
l Closed CB-2, restored P6 plug and reinstalled the motor operator for CB-l 4 back on the breaker. Transferred load to UPS power and put transfer switch in the AUTO position.
NOTE: When a trip signal is generated within the UPS it sends a shunt trip signal to both l CB-1 and CB-2. It also sends an OFF signal to CB-3 and an ON signal to CB-4.
A voltage difference alarm will inhibit a closure of CB-4.
UPS ALIGNMENT AT TIME OF EVENT:
2NPS-SWG001 2NPS-SWG003 UPSIA Normal AC (US3-B) X UPSI A Maint. Supply (US5) X UPS1B Normal AC (US3-B) X UPS1B Maint. Supply (US6) X UPS1C Normal AC (US3-B) X UPSIC Maint. Supply (US5) X UPSID Normal AC (US3-A) X UPSID Maint. Supply (US6) X UPS1G Normal AC (US3-B) X l UPSIG Maint. Supply (US6) X l
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l Page 11 1
, ATTACHMErlT 2 Niagara Mohawk Nine Mile Point Unit 2
Event of 13 August 1991 Report by:
Melvin L. Crensnaw Consulting Engineer 1
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Power Systems Engineering Department General Electric Company Schenectady, NY 5 September 1991 Sg.e#3 31
2-Niagara Mohawk Nine Mile Point Unit 2 Event of 13 August 1991 05:48 In troduction_
On August 13,1991, at 5: .
48 AM the Unit 2 phase B generator step-up transformer failed. Oscillographic records of the event are available from a digital data recorder at the Scriba Substation. They show various 345 kV 115 kV system voltages and currents. Figure A with notations is attached.
The four cycles preceding the fault show no signs of a gradual degradat developing disturbance. The oscillographic traces and station prote targets reponed, indicate a ground fault occurred on the high voltage win Depression of the 345 kV phase B bus voltage to about 39% of the prior v was observed from the oscillographic trace. This suggests the involvement of only a portion of the entire winding. The 345 kV line currents and voltage show rapid development of the ground fault beginning at point I with th current reaching a constant value of 1,300 amperes in 1 1/2 cycles at point The flashover in the faulted transformer occurs just preceding a maximum in phase 2 to neutral voltage (as would have been expected) at point 2. The 34 kV line current in an unfaulted phase increases in step function manner to of the prefault value at point 3.
No high speed recordings of voltages or currents within the plant were available. No sequence of event recordings were available to correla operation times. Due to the large amount of magnetic energy coupling the; generator rotor and stator, and known electrical parameters, the decay of fault '
current contribu:ed by the generator to the solidly connected transformer would have spanned a number of seconds as the field decayed.
i Relay operation targets reported were:
- 1. Transformer XMIB. Differential Relay (Type BDD) on Transformer 2MTX-
- 2. Transformer Neutral Current Relay (Type IAC).
- 3. Overall Unit Differential Relays (Type BDD)in phases 2 and 3.
- 4. Generator Phase Overcurrent Relays (Type PJC) in phases 2 and 3.
l
- - 3.x i.
! Postulated Event Scenario s .
- Following isolation of the generator and failed transformer from the power marked 5 on Figure A, only a single 345 kV phase to ground voltage record is l available. The magnitude of this voltage on an unfaulted phase'is 74% of the pre-fault value. i 4 Since generator neutral current is -limited to less than 8
- amperes, it is known that the faulted transformer appears as a line to line _ fault
! with some impedance to the generator. By trial and error calculation, generato line currents are found to be 0,1.9 and 1.9, multiples'of the rated value of
( 31,140 amperes. The line-to-line voltages have magnitudes 74% 74%, and 25%
! of the rated value of 25,000 volts. The decay of this voltage for 0.25 seconds of ' ,
j the recording has a measured time constant of 2.7 seconds.
~
The calculated j value of the impedance of the faulted transformer as seen by the generator is 0.23 per unit.
l Conditions prevailing during the six cycle time period following the fault, marked
~
4 2 on Figure A, cannot be determined with' certainty. The exact nature of the 1
- fault within the transformer is not known and the physical evidence will be -
4 strongly affected by the continued flow of energy from the generator due to the i inherent time constant. .The flashover of only a portion of the HV winding is evident since the 345 line voltages to neutral remain at 39%,86% and 86%'of i the pre-fault values. The presence of." residual"in the measured 345 kV line
!. . currents provides the evidence of transformer neutral to ground current. _This:
{ requires that the . fault involves a' path for current to_ ground from the high <
1 voltage winding. Recorded voltages and currents show a step change to new
! values and no dramatic change 'during the time ' period of the record, which
! totals somewhat less than 1/2 second. It could be said they are " cleaner" and - -
less distorted than commonly seen oscillograph recordings of faults, i
i Given these observations and since both the generator and the system were
- supplying fault current into the faulted transformer, generator line-to-line I voltages preceding isolation would be expected to be greater than those immediately following isolation.
I i
High Freauencv- Volinee Transfer i It has been speculated that very high frequency energy (mHz region) may hav i caused malfunction of logic and control circuitry in the~ UPS equipment. A i broad range of frequencies would be expected in'any arcing phenomenon such as occurred in this failure. Nothing in the available data or design parameters i of the plant equipment :would suggest;an extraordinary generation or
' propagation of higher frequency components. ' The failure of a transformer and internal arcing is not a rare occurrence. Comparison of oscillographic charts-i u
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from similar particular events in other plants show nothing unexpected or unusual failure.
It must be borne in mind that the sampling rate of the -
recorder is listed as 5.814 kHz and frequency components in excess o 500 Hz would not be accurately portrayed.
OE experience in testing of typical power transformers (such as the Unit Auxiliaries Transformers) provides an indication of the expected couplin between windings at radio frequencies in the region of 1 megahertz:The attenuation factors range from 1,000:
1 to 10's of thousands: 1. Direct '
measurements could be made in this plant to determine attenuation factors for individual transformers over a range of frequencies. These tests would be made on non-energized transformers 'using an RF signal generator and a sensitive, calibrated detector.
Attached recent articles on electro-magnetic interference.
Reference 1 ;
discusses. IEC 801.4 and the characteristics of electrically- fast transients.
Reference 2 discusses testing of ground connections.
-1 Station Ground Elevation The possibility of elevation of the station grounding system as a result of this t
disturbance was postulated. The relatively high level of ground fault current,-
estimated at 1,300 amperes from the available recording, would not have been ,
conducted into the plant. This current can only flow in from the 345 kV.. system l
for the 6 cycle period required for relay and circuit breaker operation to achieve! .
l isolation. The generator ground current would have been limited to less than 8 l amperes by the. neutral grounding equipment.- Elevation ~or-differences in 1 i ground this event.potential within the plant would therefore not have been expected dul !
Reference 1 discusses the problem of achieving a " super"; ground and
~
concludes that a stable ground reference for interconnected equipment is of greater significance.
Since'normally circulating ground currents are not expected, testing with very low voltages and currents is recommended. Note especially the recommendation ~ to test with a frequency 'non-harmonically related to the power line frequency.
Desien Review of Nine- Mile Point A u rillaries - Power 1 Distribution System I The transformers stepping the voltage down to successively. lower voltage levels are connected in a manner to minimize coupling of power fre higher frequency components between the - various busses. quency Specificand .
configurations are:
i
-S-1.
Normal Station Service Transformer -
delta 25 kV to wye 13.8 kV with 400 ampere resistive grounding on the 13.8 kV side.
2.
Load Center Transformers - 1 delta 13.8 kV to wye 4.16 kV with 400 ampem resistive grounding on the 4.16 kV side.
3.
Load Center Transformers -
delta 13.8 kV or 4.16 kV to wye 600 volts with neutral solidly grounded on the 600 volt side.
4 I Reserve Station Service Transformers -
wye 115 kV, delta 4.16 kV, wye 13.8 kV. The 13.8 kV neutral is 400 ampere resistive grounded. The 4.16 kV circuit is connected to a zig-zag grounding transformer with a resistor in j
the neutral connection, presumably for 400 amperes. '
These configurations provide t' effectively grounded" distribution busses as defined in IEEE Standard 142 and' will serve to limit transient over voltages This is in accordance with design practices deemed prudent and conservative within the power industry.
Transformer Failures The industry continues to review the effects of geomagnetic disturbances on power transformers. ,
While no evidence is seen of voltage distortion in the four cycles preceed failure, exc:ssive duty could have occurred if these transformers had been subjected to low level direct current previously. References 3 and 4 are attached for perusal.
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Electronics in Industrial Applications l A Discussion of Fundamental EMC Principles for Electronic Controllers In an Industrial Environment i
By William D. Kimmel, PE Kimmel Gerke Associates. Ltd
- EMC problems eth mdustna! controls are bances are a well known icdustnal problem.
aggravated by harsh environments, mixed cally a power disturbance prob:em. is oft in fact when a problem occurs. the first technologies and a lack of uruform EMC the camer of residual effects of pow thougt.t is to blame the power company, disturban:es. Any industnal or commere gwdelines. This art:cle mil concentrate on Often power cuahty is a problem (especia:Iy the common aspects of electroruc controls if groundmg issues are included). but the structure has sign:Seant :ow 'requen l m an :ndustnal env:ronment, which is currents arculating through the grou generally much harsher than the of5ee problem is almost always generated by system. sometimes because the energy adiacent equipment.
environment. intentionally dumped onto the ground (su Traditional problems with power include What is the industnal environtnent and spikes and transients, sags and surges. and as with an arc welder) and sometim what can be done about it? The em tronment because of unmtentional couphng or ev.
outages, which threaten the electrorucs via mcludes the enure gamut of the basic the power supply. These problems are an inadvertent connection between neuu threats. power disturbances. RFI. and fairly well documented and are often solved and ground somewhere in the facdity.
ESD. RFI and power disturbances may be Radio Frequency Interference. R using power conditionen or UPS.
ba!!y generated or not. Mixed technolo- dio frequency interference affects bo The most common power problems analog and digital ciremts, with analc gies cocund the problem. Digital circuits confrontmg electronics today is the sag circuts being generally more susceptibh are used to switch Ime voltages via relays. which typically occurs dunng turn en and Analog sensors are mput devices to digital Surpnsing to many, the prmople threat .
controls, the spikes which typically occur dunng turn off of heavy inductive loads. "he sags not the 'IV or FM station down the roac Increasingty, there is a need for a but rather it is the hand held transtn:tte simply starve the electronics. The high camed arouno by faalices personnel. A on.
- ooperaove effort between the designers. frequency transients barrel right through manufacturers and installers to co_me up the supposedly filtered power supply to watt radio will result m an electnc 6 eld c with a rock. solid system. A common five volts / meter at a one meter distance attack the electronics inside.
complaint is that the mstallers or mainte- Digital circuits are most vulnerable to enough to upset many electrorucs systems nance people won't follow the installation IEC 801.3 spec 5es imrnurury to electn spikes which cause data errors or worse.
reqwrements. This may be true, but it Analog arcuits are most vulnerable to Belds of one to ten volts per mete must change. smee there are problems depending on the equipment, with thre conunuous RF riding on top of the power.
which cannot be solved at the board level. volts per meter being the level for typic:
FIPS PUB 94 provides guidelines on equipment. As can be seen from the abov It is also ' rue that manufacturers often electncal power for commercial computers.
specify installauon requirements which are approximation, three volts per meter is nc His is good information, but beware that an excessive requirement, and even te:
not practical to implement, and there are factory power is much noisier than commer-documented cases where the prescribed cal power. volts per meter is fairly modest.
instal! acon procedures wid cause rather Electrostatic Discharges. Electro-than cure a problem. The guidelines of IEC 801.4 rpeci5es an static discharge is an intense short duracon electrically fast transient (EF'i; that simu- pulse, harmg a nsetime of about The lack of uniform guidelines has ham- one lates stems and other high speed noise, nanosecond. His is equivalent to a burst pered EMC progress in the indust:ial arena. Fortunately, the European Commu.
EFTS are quite short ranged - they of 300 MHz interference. Staue buddups dimmish rapidly with distance due to induc.
ruty is working to adopt the IEC 801.x of 15 kV are not uncommon.
tance in the line. But at Short range, they Dry climates, including northern climates specifications, and domestic compacies are devastatmg.
would be wise to adopt them, even if there Unfortunately, attention is placed on the is no intention to export.
I front end of the electrorucs, the power William Kunmelis a pnnapal wrth Kimmel The Basic Threats supply. With industnal controls, the prob. Gerke Associates, Ltd. The Erm spenal-The three basic threats to industrial lem is the controlled elements. If the ises in prerecong and solving electromas-electrornes are power disturbances, radio electronics is controlling line power, the neoc intederence and companbibry (EMI/
frequencyinterference. and ESD. disturbances sneak in the back end where EMC) problems. Mr. Kimmel can be little or no protection exists. reached at 1544 N Pascal. St. Paul, MN Power Disturbances. Power distur- System ground, while not being specs- 55106, or telephone 612-330-3725.
EMC Test & Design 35 t
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Figure !. Amph5er demodulation.
Figure 2. Trans>ent feedback path.
m w mter, offer opportunity for ESD. encounters a nordineanty such as a semicon.
Industnai environments, w:th the:r movmg to heavy equipment, whJch is character ductor device. A!! such devices give nse to by heavy startmg l cads and inducuve equipment, are loaded mth potential ESD sources: rubber roDers, belts, and produc. a DC level shift when confronted mth RF. at turn off. Typicany the e!ectroruc con In a radio receiver they are caBed detec-tion output such as plastic and paper reus, switch line power utmg relays or tr a:1 add up to a real ESD threat, and this tors. Nordineanoes are mirumized in liacar - This exposes the back end of the con devices. but there is always enough to cruse to substcntialline transients, which ec threat is more hkely to occur even m problems. The upshot is that the amph5er back to the ciremt power and ground relauvely moist environments. I.ook to IEC demodulates the RF, generates an errose- disrupt the distal ciremtry as show 801.2 for ESD standards.
ous signal, and passes this error on. This Figure 2.
effect is shown in Figure 1. Output lines are It is mandatory that the transient Electronics Design Electronics is generacy the uiumate simdarty affected, with capacitive coupling back to the mput, rents be diverted or blocked. since vicum of mterference. The interference digital system cannot mthstand the ma The solution is to prevent the RF from tudes IIkely to occur with an educuve k finds :ts way through various paths to the electrorucs eqwpment its?If. Let's concen- gettmg to the amph5er, either by shielding uniese special steps are taken.
or Stenng. The most common path to the Self Jammmg can be lirruted by control trate on what can happen to your electronics ampli5er is via an external signalline from from the back door, that :s. by direct when you switch the line, usmg 2 the sensor, but if the electronics is not crossing devices. Of parucular importa.
ratauon into the electrorucs and by con-ducted sterference through the signal and shielded. direct radiat on to the circuit board is the turn off, since that is when may also present a problem, control bnes. inductrve kick occurs.
Assunung Stenng is the selected method, If aH power switchmg used zero cross Sensors. Low level sensors such as use a lugh frequency Ster, designed to thermocouples, pressure sensors, etc., are devices, the transient levels in the fact.
block signals up to 1 GHz or even trore. would be dramaticaDy reduced. Unfot charactenzed by very low bandwidths and 4 Use femtes and high frequency capacitors. nately, that goal is well off in the futu low s:g':a! levels. A major threat to these l Do not rely on your low frequency Star to Until then. expect that high voltage pos sensors is radio frequency mterference, take out RF. !
either from nearby hand held transmitters transients will occur, and they must be de At the op amp. you should also decouple with. )
or more distance land mobde or f:xed your plus and mmus power to ground at the 1 transtrutters. Optical couplers and relays do not prov chip. If your ground is carrymg RF, you can sufficient isola 00n by themselves. Th But these are high frequency, much anticipate the same problem mentioned {
above the bandpass of your arcph5er, right?
high - provides an exceuent h: '
above, since it wd! corrupt the reference frequency path, and if they are stacked Wrong! Low frequency amph5ers are level.
plagued by two phenomena: out of band in an array, the capacitance m0 add up Data Lines. Digital data lines will be peas surprisingfy low frequences. The response and audio recuScation. These upset by the RF problem as in analog, but capacitances can't be ehminated, but y<
combine to provide false information on levels to the system. the levels necessary to upset are higher, can design your control circuits to muunu.
Instead, digital data lines are much more All amplifiers have a normal bandpass, coupleg paths and to maximize low unpe susceptible to transient glitches. AI signal ance attemate paths.
typt5ed by a 20 dB/ decade rolloff or more lines should be Stered to paas only the Trsasient suppressors should be instaUe at the high end. But resonances due to stray frequences necessary for operation. If the mductance and capaatance mU give nse to at the loed, which is the source of the spik.
threat lies in the bandpass of the signal, but they can be insta!!ed at the controue amphfier response Sve orders of magnitude then shielding or opucal links will be or more above the nominal bandpaas of the as we2.
needed.
arnplifier. This means an audio amph5er An interesting effect occurs when con wdl respond to signals m the hundreds of Switched Power Lines. His refers bining zero crossmg SCR regulators mt MHz. specfically to the power being controDed low level sensors which use line frequene by the controller device. Induatrial control-The second aspect occurs when RF noise canceling techmques. Very sens:uv lers are commonly tasked to control power sensors sometimes are sampled for a 36 My M: gust ?
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Figure 4. Muluple ground paths.
entre power cycle to cancel the line frequency component. If the samp'e occurs More citen the problem is conducted.
either via power or ground. The problern eliminate RF or g ound noise. That concurrently with ;ine power switching on work, but these problems can be so occurs due to power and ground distur-or off, the average to the sensor will be with an isolation transformer to e!imi upset, and an error wdl be recorded. bances caused by the equipment. It is an all too common pract;ce to draw contro!!er neutralto ground noise and mth EMI po power from the same source as feeds the line Siters. So you may want to try System Design and Installation inexpensive approach first.
Once the electronics is designed, it power eg.upment. This power may provide the necessary energy to dnve the equip- Data Links. Data links are strung becomes a problem of the system integrator over the entire fact!ity, exposing therr ment, but it is not suitable to power the and insta!!er to ensure that the electrorucs electrorucs (Figure 31. two prtnciple effects, ground noise and is provided mth the environrnent for which pickup. Ground noise mD cause data ert Hopefully, all industrial equipment wiu it was designed. Most of the time, this unless the electronics has been designet work is performed by power experts and have electronics powered from a separate accommodate potental differences of s low power 120 volt circuit. It solves several electncians, and they are not always aware eral volts or more. This is accompi:st problems. First, it separates the electron-of the mterference problem. Often, on site. mth differential dnvers and receivers tf t!
the power quality is blamed for the equip- its power from the. probably very noisy must be direct coupled. Optical links -
ment anomahes. But the problem can often industr:al grade power, preventing the eventually take over these links.
be avoided by followmg a few basic prmes.
smtching transients and startup sags from gettmg to the electronics. Second, if it is The other aspect is RF pickup. Icexpe ples.
necessary to condition the electronics power sive shielded cable is suitable for t.
The mdustrial control device is either from an external problem, it is far cheaper purpose. Ground both ends! Do not apt integrated into a system at the factory or smgle pomt ground techniques to RF. It instared separately on site. Controuers to condition the watts needed for electronics low frequency ground loop problem is handle a vanety of devices such as motor power than it is to condition the kilowatts required by the system. threat, then one end can be capacmve speed controls, positioning devices, weld- grounded.
If power cannot be separated, then it is ers, etc. Interference presented to the electrornes can be sigm6cantly reduced by necessary to provide a bulletproof power Summary appropriate measures outside of the elec-supply, preferably including an isolation Industrial electronics are subjected to I trenics box, transformer. to separate the entire power harab environrnent. Good design and inst.
supply from the electncal equipment.
There is no way to accurately assess the lation techtsques will mirumtre problems threat mthout test data. But regardless of Ground Noise. Ground noise, inevits-ble in industrial environments, must be the 6 eld. Adherence to the Europe:
the mformation available, much can be standards,1EC 801.x is a good start. eve accomplished by correct instaBation, and it diverted from the electronics module, if you are only marketing in the USA, s Multiple grounds in a system wil often doesn't cost much if done at the start. result in ground currents circulaang through Retro 6ts become costly, especiaDy if ac- Bibliography comparued with factory down time, the equipment, and ground noise circulating FIPS PUB 94, Guidelme on Electncs let's consider the same problems from through the electronics path wiH cause <
Power for ADP Instauauons. Septembet I a system standpoint. Your goal is to limit malfunction. Figure 4 shows some typical 1983.
ground loop situations.
the interference which must be handled by IEC 8012, Electromagnetic compatibilit'.
the electrorucs. A common approach is to demand a super for industriabprocess measurement an(
earth ground. This is good, but it is not a Direct radiation to the electrordes is not cure all, and often a super ground cannot control equipment. Electrostatic discharge often a problem in an industnal environ- requirements.1964.
ment. but it does occur, and most often with be achieved, no matter how you try How do you get a super ground from the third IEC 801-3, Electromagnetic compaubilit) .
a plasoc enclosure. The NEMA type door? The reat need is to get a stable ground for industriahprocess measurement anc enclosures provide enough shielding for control equipment. Radiated electromag-reference to allinterconnected equipments. netic 6eid requirements,1984.
most mdustnal needs. If you don't want to If this equipment is closely located, then a use a metal enclosure, be sure to get very low impedance interconnect is feasi- IEC 8014. Electromagnetic companbi!ity electronics which mu withstand the RF ble, for industnal-process measurement ar.s which mil occur. contro! equipment, Electncal fast transienu Power conditioners are often tasked to burst requirements.1984.
EMC Test & Deun
REFERENCE 2 Industrici Equipment Equipment Ground Bonding -
Designing for Performance and Life )
A Discussion of Ground Connection Fundamentals to Con By D.B.L. Durham Dyteena Ltd. UK The problem of achieving sausfactory earth bonds or ground connect 2ons has plag.ted eqmpment to a stable ground point achiev.
ing adequate levels of cable shielding and for inductance. At very high frequencies EMC eng:neers for many years, not only stray capacitance across the strap many other reasons. Many designen un-because the bonds are often vital for the dommate. This means that the volt d; achievement of satisfactory equipment pe6 derstand the requirement for short, fat bond leads to minimtre gmund inductance but across a bond is generally a function formance but because they affect the long inductance and frequency. Based on Ohr.
term performance of eqwpment after it has few appreciate that a critical aspect is the Law this volt drop is shown in Equaton been introduced mto service. connecuen resistance with which the bond strap is attached to the equipment ground For transients the voltage drop as given Recommendacons on bonding have ex- Equanon 5.
isted in the form of mditary specificanons, pomt. The basic requirement of any bond is that it should have as low an impedance 7 ,j VR' + w L82 such as Mil Std 1310. MH 188-124A and as possible (unless it is a deliberate induc. i Md-B 5087 (ASG) for some years and these have genera!!y proved satisfactory for most tive bond to limit ground currents). The impedance is a combination of the resistive Y*II"NU (
i new builds. However, these spec 5 cations have certam limitations in that they gener- and the inductive components. The resis-ally do not speedy consistently low levels tive element is a function of the bond strap y = -L y (
of bond impedance, nor a suitable test resistivity, cross sectional area and length, see Equation 1 whilst theinductive compo- where Z = strap impedance, w = rada.
I method. The introduction of new EMC nent is a more complex function of the bond frequency, V = voltage. and ! = current, specificanons in Europe with the EEC i strap charactenstics as shown in Equation 2.
From this, the higher the mductance th. ;
Directve on EMC and the requirements for i more isolated the circuit or box become R=g i
4 long tenn stability in EMC characteristics from ground. This can have sign:fican has directed the UK military to review ^ (1) e5ects on eqtapment. including enhance exisung specScations and introduce a new mest of nonne iniection onto occuits, redue
- Defence Standard to tighten up perform- i L.&; 2f C tion of fDter performance, and loss o ance requirements for military equipment. in + 0.5 + 0.2235 2n , b+c commention range. From a TEMPES1 2f ,
Def Stan 58-6 (Part 1)/1 has been intro. standpoet it may result in more radiauer duced to address this area as far as mobile (2) from eqmpment. It would seem from this and transportable communications insta!!a. that the entens for any bond is the i tions are concerned, but the reqmrements where R = resistance, a = resistivity, f=
j length. A = area. 4 = permeability of free inductance and hence the choice of sho should have implications in industnal appti.
4 cations and over the whole electromes space. L = inductance, g = relative David Durham served for 22 years in the market iflong term product performance is permeability, b = strap width, and c = strap Birash Array, where he to be guaranteed. thickness.
in electncal eagmeenng. gaswd his de Alter service in a The frequency at which the inducuve Bond Degradation element dommates the impedana expres. vanery of appostments be retired to join sion when calculating the totalinductance the RacalSES company as the Techmcal Earth or ground bonds are generally Afaneser responsihie for the design and is, from Equation 3. typically 1 kHz. It wig considered essentia$ not only for safety development at communkstion systems.
reasons but as a means of divertmg EMI be seen therefore that to aB intents and la N bejamed Dyrecna as the 5fager currents. " locking" careuit boards and purposes the bond except at DC and power frequencies, may be assumed to be an of the Ensmeenns Division, and now is 38 currently Technica/Marketmg3fmger.
July / August 1991 d
C 4
i ,
, ec. o sesiswcr . s'. 42 I EaMsisw:r es ap.*asrER -
Cipme M N ttT h n ac,-W l
\
/
As w
- i
! i / @
\i to lo amos -
l s y
,/
p *as-te aas*<a ' l f / %\ ,
i
, -- : / g t
scaec s'ea e /
$- f W T f
\. f. h R I i 1 -
i=r g
y Figure 1. Bond resistance. _i Figure 2. Four wire bridge method. '
bcnd straps. However, an analysis of :he bond inductance shows that for a bond strap progressive degradation of bonds, whilst
! the latter can reduce the efficiency of the current the layers heat up and are vapo. ;
of 100 mmlong,15 mm mde and2 mm thick
! bond from the moment it is instaued. It is can nsed. After the current is removed the film i the impedance at 1 MHz will be 3.8 Ohms. return. Thus high current techmques 1
It sounds extremely sirr.ple, but work parucularly important in commumcations ,
l systems, where Sters are instaDed and are not recommended for tesung EMI I performed in the USA and UK shows that shielded cable ternunations are made thatUK specSesnew bonds. De Defence Standard in the . I tf an error is made in the way the strap is a maximum probe voltage of ternunated then a progressive increase in the bonds are their performance.
oflow resistance and retain 100 microvolts. His represents typica!!y a
)
the resistance of the bond strap to box probe current of 50 miHiamps under short juncuan can occur as the equipment ages.
EventuaHy the resistance wtB begm to Bond Performance and cirest (< 1 mG) conditions. This is i Measurement meuscient to destroy surface sms. The !
exceed hundreds of ohms and may eventu- classic method for measuring low resistance ally go open c:rcuit. This can negate the Expenence has shown over a number of j effect of the bond strap completely as part years that for long term consistent bond has been to use a four tenninal bndse as ;
shown in Figure 2. In this case the current of the EMIprotection. performance a low value of resistance must . is drtven between . two poin!
i What happens with bonds to cause this . be achieved. Bis is typically 15 nuDiohms.
voltage across the sample is measured mth change? Essencally a ground connectaon is In Def Stan 56 6 (Part 1)/1 the value hasa high resistance probe. This removes the -
a senes of impedances from the strap been set at a maximum of 2 mdbohms. nis e5ects of the probe contact resistance and through to the ground matenal as shown level is measured through the individual bonds. The logic behind this level is ' lead resistance. His is generauy consid.
in Figure 1. Each point of contact contnb- ered to be a laboratory method as the use -
! utes to the total bond performance. As a twofold. Firstly, experience has shown that with communications equipment in particu- of four contacts can be awkward. If the lead result, a change in any contact condition can resistance can be removed by a calibracon .
result in a change in the total bond lar this value of bond resistance is requred if consistent performance is to be achieved ' techaque then the four terminals may be resistance. As is weH appreciated, the repisced with a two terminal system.
in terms of reception ef6ciency and trans-contact resistance between two rnetal sur- A further possible refinement to the faces is a function of the pressure. De mission characteristics. his is i J.d techaque is to use a frequency that is not so for TEMPEST protected equipments.i pressure exerted by the tip of a drawing pin DC or 50/60/400Hz. In this case 10.4 Hz is vastly greater than that from the thumb ne second point is that if the bond has a ,
bisher resistance then there is a pena 5 cant has been chosen. If an acove filteris used j pressing by itself. Thus the contact from a to Star out au other electrica! noise, then '
likelihood that progressive degradation wW sharp pomt grves a much higher pressure it is possible to use the bond resistance than a flat point and therefore lower contact occur and the bond resistance wilincrease sneter on powered up systems. It is worth in value. There wig then be a progressive resistance. Measurernents have shown that loss in performance. noting that at this frequency the impedance sharp points enable contact resistance of a _
is stiB largely represented by resistance -
i The mam problem with inessunne bond few r::icroohm to be achieved whilst similar rather than inductance. The two termma!
pressures on flat surfaces result in mil- resistances is that it should be measured method is shown in Figure 3.
i lichms of contact resistance. It might be using a low voltage / current technaque.
The introduction of. new EMC/EMI Most techniques to date for assessmg safety specdications in Europe has made it more felt that there is little or no diference involves driving a large current through the between these values. but in reahty there unportant that once made the bonds have is. An essential aspect of a good bond is bond. This checks the bond's abihty to consistent long term performance. This carry current but does not necessanly check that it should remam so after the equipment means measurmg on penodic inspection and has entered use. High pressures also have its EMI protection performance. The rese after memtenance, it is an essential aspect the effect of squeezmg out corrosive maten- son is that many bonds may when in normal of insurmg conastent performance, it has use have a high resistance due to onde and als and insulatmg Ems. The former causes been shown that within months apparendy greasy Sms. but when subjected to a high good bonds can detenorate to high resis.
EMC Test & Design 29 i
i -
i i
4 4 ,
4 i
- amor 3g;ro.,
tance. Therefore 33 :y;es of bence j suoject to testing and exa=nabcn :n s i
}
) W vc;?ase weasvoweNT I' }
as a ma:ntenance taso j , O j UK Military Experience
}
i l
! h h Ni f There have been two major ;re caused by poor bonds expenenced ;
4 rinco ecs.stANet by md ary eqummen: asers. The nrst j ,f degrada: ion .n perictmance &eady i
j
- i j tiened m ttus article. The loss of ecm cauon range. poor EMI performance
' A' '
other effects all con:nbute to a cons:
- l reduct on m equement effaency and .
1 l
i ability. The second effect which is .
- difficult to idenufy is that of No Fault F j .
i i (NFF) problems. An analysis of repc
! faDures from military reliabGty data
} I -
shown that NFF incidents can be e
! I ~FlXED RESISTANCE LEADS high, parucujarly in humid chmates.
- l d p.___
has been partially confreed by repons :
the Gulf War when a!! forces reportec
- g
---I increase m svadabdi:y of equipment ;r.
g dner chmate. Many faults are due to
$ electncal contacts in connectors, but a la j Figure 3. Two tennmal bndre method.
nurnber have been idenufied as exces-EMI induced through poor ground bor
- This may be caused by e
- ther a loose gro I strap or connector terminacon to the t a a A signiScant unprovement ;n equgm i' 0 $ availabQity and performance is expec
@ when more recent stausces are analysec
$ The introduction mto the Bnusn Ar
} e service of the Dyteena Bond Resistar i 1 g c g Test Set - DT 109 has enabled the l mditary to measure bond res: stances
- ^ Ms8 e
installed equipment and reduce the c i
9 A** M' A curances of NFF errors. The UK mdita
,g, ,gs.poE y g* ge .
0\
measurement procedure uses a two :erir nal bndge method and an accurate g#"4* o9
,o\ mEchm cahbration standard. Th:s mea .
, .g p. a urement procedure and equipment is ah 1
ot y **
p p,,8W gg in use by other NATO nations and e!s, where by rmbtary and naval forces who has
,A '
recognized the same problem.
2*
e ((
ge # +ov
{ p Y 96 Conclusions ot%ge 9 **p4 Colt
- d Mg@g/e# c ,
V V The problems with ground bonds hav i
- Comr) ham e CUSTOMlZING Ts 4
, y$ f ,9g 8".#
t+ * # .
. hrs w es become sig:u5 cant with the development c sensitzve and secure commurucanons equm i p .slON ment. This coupled with an incressmg neet j
COMPAC RF At. Ao'p> to achieve higher and higher levels of EM Coaxial Terrn. # #s# ,sA*f., nuators, snnectors, protection has lead to an mcreased emphasa
. bems placed on the effectiveness of all types j
Cata of system grounds. These, funher com-1 . quest bined with a requirement to ensure the long
- hfe of systems once m service, have
(( . a resulted in the assessment that bonds and
- termmations are one of the pnmary causes 1
1Ut%12 bncoln Avenue. Hoibrook. NY 11741 of EMI faDures in systems. The require.
6%);B5-1200 f AX ;164851914 ment to test these is clear, however the
] means to do so have not always been j 40 INFO / CARD 29 avadable to engineers. T
, Jahs Aur.st l991 t
b
_ _ _ _ _ . _ _ _ _ _ - - _ _ - . _ , ~ _ _
a REFERENCE 3 1
3 l
i l
1 4
! l 1
1 j I
, i
.n n . . .
- ' hyhfHh Q I ' (phi 9 @ 't u g.
~
I' :
- /
- ir M .' f b M KW "
1 . mQLw_ ..:. m- , ii t)(g
., m y ~Q.>L.y,?w
- u. ..
i -
d 4
$ Panel Session i PES Summer Meeting, July 12,1989
- Long Beach John G. Kappenm, an,California Chairman Power System Susceptibility To Geomagnetie Disturbances
- laduc'd currents in the system, 2) the interconnected sys-tems tend to be more stressed by large region-to-region Present And Future Concerns tr.nsfers, combined with GlC which will simultaneously turn j
'""Y"***'i"'"'6"'""**'"' ''"*""'
power consumer and harmonic current generator and 3) in general, large ENV transformers, static var compensators and i relay systems are more susceptible to adverse influence and John C. Kappenman, Minnesota Power The effects of Solar-Geomagnetic Disturbances have been found impact of the Marchobserved for decades.on TRANSFORMERpowerOPERATION systems. However, the pro-bance has created a much 13.1989greatergeomegnetic distur-level of concem The the about primary concem with Geomagnetically-induced phenomena m the power industry. rents is the effect that they have upon the operation of large ower transformers. The three ms Several man-made systems have suffered disruptions to their in transformers dlevar il the incrosse)or consumption of theeffects normal operation due to the occurrence of geomagnetic phe-transformer,21 the increased even and odd hermon-affected nications, have been made less susceptible to the bilities of equipment phenom-nomena.
damaging stroy flux heating. As isMost well ens through technolog! col evolution (microwave and fiber- - documented, the presence of even a s
, optic have replaced metallic wire systeine). However (20 the empe or less) will cause a large power transformer to 4
bulk transmission system, if anything, is more suscep,tible hatf-cycle saturate. The half cycle saturation distorted excit-today than ever before to geomagnetic disturbanceIng events current is rich in even and odd hermonics which becom And if the present trends continue it is likely the bulk .
trans- to the power system. The distortion of the excit-Introduced mission network will become more, susceptible in the future. a6so determines the real and reactive power re-ing current Some of the most concoming trends are:
- 1) The transmission quirements of the transformer. The saturation of the core systems of today span greater distances of earth-surface- steel, under hetf-cycle saturation, can cause stray flux to en-potentist which result in the flow of larger geomagnetically- ter structural tank members or current windings which has IEEE Power Engineering Review, October 1989 the potential to produce severe transformer heatino.
15
, .~ m .. _m . . . . . . _.. . __ _ _ __ . _- _-_
. .. . ~ . o .mr fee tests on ex-isting large power transformtts to evaluate the response o'. ' hemtsonses. Th@ auroral el;ctrojets can oroduce transr2r diffsring transformer core types. The field test results in@* fluctuations in tM3 carth's magnetic fleid that are termai . ,
cafe that smgle phase transformers half cycle saturate much geomagnetic storms when thay are of sufficient severityc 3
more easily and to a much greater dagree than Comparable
[
inree phase units. These transformers produce higher mag- SUNSPOT CYCLES AND GEOMAGNETIC '
- nituces of harmonics and consume larger amounts of resc- . ,
I i
tive power when compared with tr.ree phase designs. >
On the average, solar activity, as measured by the number of i RELAY AND PROTECTIVE SYSTEMS monthly sunspots follows an 11-year cycle. The present 1 sunspot cycle 22 had its minimum in September 1986, and There are three basic failure modes of relay and protective is expected to peak in 1990-1991. Geomagnetic field dis. .
systems that can De attributed to ggeomagnetic distur- turbance cycles do not have the same shape as the sunspot '
bences:
number cycles, even though they are cyclical. Figure 1 shows
- the nature of the sunspot numbers and geomagnetic activity ,
False Operation of the protection system. such as hav- !
ing occurred for SVC. capacitor and line relay opera-tions where the flow of harmonic currents are misin- svag
- taat.tess y;Q' - {
terpreted by the relay as a fault or overload condition. aos crm ir cym to cym is cnie 20 cnte 21 ce,sa.., -
This is the most common failure mode, I , as a as I I I I
Failure to Operate when an operation is desirable. this **""*** **f****'
has shown to be a problem for transformer differential # N
- f protect;on schemes and for situations in which the f 120 output of the current transformer is distorted. ,
l;
{j lm :
Slower than Oesired Operation, the presence of GlC 0
y a; .
fj ,\ l .l can easdy build-up high levels of offset or romanent l '
- ', #. D ,\ '6 '
l
- l'I(?)t ' f **
tium in a current transformer The high GlC induced off. se (
g l 1-( ./ (
=a,
, set can significantly reduce the CT time to-saturation. i*
V,, > 4e for offset fault currents. '
3
- Most of the relay and protective system misoperations that are attributed to GlC are directly caused by some malfunc- h M " W " A W "E T E T ys*"s'E"E~~sb tion due to the harsh harmonic environment resulting from - 1.
large power transformer half-cycle saturstion. Current trans- ens of me Yeady-Aweeed Sunepct Number and 'i
!- n Dieturbed Deye from 1932-1988. ;
former response errors are more difficult to directly associate '
with the GlC event. For example in the case of CT remen- ..
i ence, after the the GlC event CT response that producederror may notTherefore, the romanence. occur until several days cycles from 1932 to 19861'
! these types of failures are more difficult to subetontiste, disturbance cycles con have a double peak, one of which can -
leg the sunspot cycle peak. While geomagnetic activity in the )
CONCLUSIONS present 1993-1994, cycle is expected to maximise in approximately :
As evident by the March 13th blackout in the Hydro Quebec a strik8 g exempie; time during the cycle; the K 9 storm13,1989 of Marchsevere was system and transformer heating failures in the eastem US, longe. The power mdustry is more susceptible thanP ever -
TENTIAL tothe AND power industry is f '
the influence of geomagnetic disturbances. And the mdustry CEOMAGNETICALLY. INDUCED-CURRENTS will continue to become more susceptible to this phenome. _j non unless concerted efforts are made to develop mitigation The euroral electrojets produce transient fluctuations in the techniques. !
earth's magnetic field during magnetic rtorms. The earth is '
e conducting ophore and portions of it experience this time-varying magnetic field, reeutting in an induced sorth swac e- i Geomagnetic Disturbance CauseS potential (ESP) that can have values of 1.2 to 6 vo'tokm (2 l to to voitsimine> durin severe geomagnetic storms m re-I And Power System Effect$' 8"' '"** **"" **"*g *""'*Y'*'
i Vernon D. Abertson Electric power systems become exposed to the ESP through the grounded neutrals of wye connected treneformers at the University of Minnesota oppoelte ende of long transmission lines, se shown in Figure i
i
- 2. The ESP scte se en ideal voltage source irnpressed be-
- tween the grounded neutrais and hee a frequency of one to SOLAR ORIGINS OF CEOMAGNETIC STORMS a few mehens. De goemagnetically-induced currents (GtC)
The solar wind is a ratified plasma of protons and electrons are then determined by dividing the ESP by the equivalent dc resistance of the paralleled transformer windings and line flares, coronel holes, and disappearing filamente, and the so-cmrfted from the sun ,
lir wind particles interact with the earth's magnetic field to ' neutrals, excess of 100 emperos have been measured in produce eurotel currents, or eurotel electrojets, that follow generally circular paths around the geomagnetic poles et al-titudes of 100ofkilometers or morein(1).
the The eurora borealis is - - POWER SYSTEM EFFECTS OF G visual evidence the euroral electrojets northern
. 16 The per-phose GlC in power transformer windmgs can be IEEE Power Engineering Review.' October 1989 i
o g
. _-_. .._ , _ _ _ - - . _ _ _ _ . . - , . - _,m m.. .. _ - , .
9' 1
fi /
4 i ~
g' and retuced cause tim 7-to-s:turstion relay misopfration (5), in currsnt trans s
^
A \j REFERENCES
- i a t'** 1. Akosofu, S..l., "The Dynamic Aurore." Scient:fic Amen.
East.e scaract ,g j ,
Magazine. May 1989, pp. 90-97 i
? -EARTS$# ACE SQTENT'AL - t 2. Joselyn. J. A., "Real.7,rne Prediction of Global Geom ,
Fisure 2. Induced Earth Surface-Potentist(esp) Producins Georneg- Activity," Soter Wind Megnetosphere Coupling. pp. 12 notically-induced Cunente (G1 Clin Power Systems. 141 Terre Scientiflc Publishing Company, Totvo,1988.
3 Thompson. R. J., "The Amplitude of Solar Cycle 22 " r Radio and Space Services Technical Report TR-87 03.
cor 1987.
many times larger then the HMS ac magnetizing current. re. 4 V. D. Albertson and J. A. Von Boeien.'"Electnc and ,
sutting in a de bias of transformer core flux, as in Figure 3. Fielde et the Earth's Surface due to Aurote '
Transections on Power Apperatus and Systems. vol.
No. 2. April 1970, po. $78-584 I 5. J. G. Koppenmen. V. D. Albertson, N. Mohen, "Cu e{ Treneformer and Relay Performance m the Presence 4j magnetically. induced Currents,"1EEE Transactior e on Pow j; Apparatus and Systems. Vol. PAS 100. No. 3, pp.107 toes. Merch 1 set.
lI ,
T, The Hydro-Quebec System la
. Blackout Of March 31,1989 to.oi jetc),,
Q .
y
. Danle! Souller, Hydro-Quebec -
On March 13, t g8g, an exceptionally intense magnetic stom Fleure 3. DC eles of Treneformer Core Flus Due to GIC. caused seven Static Ver Compensators iSVC) on the 735-kN network to trip or shut down. These compensatora are es i sential for voltage control and system stability. With theit.
loss, voltage dropped and frequency increased. This led to The half-cycle saturation of transformers on a power system system Instability and the trippmg of all the La Grande trans.
is the source of nearly aH operating and equipment problems mission lines thereby depriving the HQ system of 95 >
Quences of the half-cycle transformer saturation are: caused by GlC'ssystem .
during ,
Theharmonics transformer becomes a rich source blackout ofcolgwreting even and affected stations. ad but a few substations isola odd e
A great increase in inductive vars drawn by the trans. Power wee graduelty restored over a nine hours period. De-former lays in restoring power were encountered because of dam-. i Possible drastic stray leakage flux effects its the trans.
- aged equipment on the La Grande netw former with resulting excessive localized hosting. -
There are a number of effects due to the generation of high SYSTEM CONDITION PRIOR TO levels ings of harmonics by system power transformers, includ-Total system generation prior to the events was 21500 MW, Overloading of capacitor bends most of it coming from remote power-generating stations at Possible misoperation of relays u Grande. C m and Churchm Ms. Exports to -
- Sustained overvoltages on long-line energization Higher secondary are currents during single-pole werewas work on loded DC interconnections.
at M of its stabWty The HmA 736-kV transmissi switching . .
- Higher circuit breaker recovery voltage Overioeding of harmonic filipre of HVDC converter ter.SEQUENCE OF EVENTS minals, and distortion in the ac voltage wave shape At 2: 48 a.m. on March 13,~s very intense magnetic storm that may result in loss of dc power transmission.
led to the consequential trip or shut down of seven SVC's, The increased inductive vars drawn by system transformers Containing me impact of me event trough opermor inter-during half cycle soturation are sufficiert to cause intoior- vention wee impossible ed SVC's hovmg tripped et consed to MVAR flow on transmission lines, and problemss.)with - gener.able system v after the lose of the last SVC, all five ator vor limits in some instances. '!
- 735-kV lines of the La Grande transmission network tripped '
. In addition to the half-cycle saturation of power trans- due to an out of step condition. These line tnps deprived the formers, high levels of GlC can pro 6sr.e a distortea response system of 9500 MW of generation and subsequently led to a complete system collapse.
IEEE Power Engineering Review, October 1949 17 .
_ .. - - _, - _ . - ._. - _ . . _~ , _ . - _ _ . _ ~ . . _ ,
'^m W 3I ADL C .WE. MAT R TRImNCS Three SVC's w:re tnoo:c by capacrtor current overtoad pro- {ffectS Of Geomagnetic taction wnle remaining four SVC s shut down by capacitor voltage unbalance protect:on. Analysis of vcitage and cut- DiSttirbanceS On Power Transformers rent escillograms taken at the Chibougamau site before the SVC rnos showed the following harmonic contents. Robert J. Ringlee AC AC Current at 16 kV James R. Stewart Harrnonic Vcirage Power Technologies Inc.
Order at 735 kV TCR Branche TSC Branche This discussion addresses the effects of geomagnetic distur.
1 100 *, 100 ", bances on power transformers. The primary effect is due to 2 ; *, 100".
9% 38 % core saturation resulting from geomagnetically induced cut-3 2 ", 12 ". Ma rents. GlCs. Core saturation can impose severe temperature g 3,, problems in windings, leads, tank plate and structural mem-6 l ', bers of transformers and place heavy var and harmonic but-1 *. 16 %
7 0 *. 3 ". dens on the power system and voltage support equipment.
4% GlC's of 10 to 100 amperes are more than more nuisances !
QuasnDC currents generated by the magnetic disturbance, in the operation of power transformers, the manner of flow saturating in the SVC coupling transformers are thought to can result in saturation of the core and consequent changes be the cause for such a large second harmonic component of in system var requirements, increases in harmonic current current in the TSC branch. magnitudes, increased transformer stray and eddy losses.
and problems with system voltage control. ,
l GENERAL OBSERVATIONS ON THE SYSTEM BEHAVIOR CIC EFFECTS VERSUS CORE AND WINDINC CONFICURATIONS The system blackout was caused by loss of all SVC on La Grande Network. Seven SVC tnpped or stopped functionmg. Principal concems in this discussion are for E i
! Prior to and during the event all the DC interconnections be- with grounded Y transformer banks providing conducting ;
haved properfy. No relay falso trips or misoperation of special paths for GIC and zero sequence currents. Core and w protection systems were observed. Telecommunications configurations respond differently to zero sequence open.cir.
were not affected. No equipment damage was directly attrib- cuit currents and to GlCa. Note: as used here, the ter utable to GlC but once the system split. some equipment was circuit" refers to tests performed with all detta conne damaged due to load rejection overvoltages. opened or broken. For example, the three-phase three leg core form transform,ers are less prone to GlC induced satu-ration than three phase shell form transformers. But, both REMEDIAL ACTIONS TAKEN core form and shell form single phase transformers are sus.
ceptible to GIC induced saturation.
Since the event, the following actions were implemented:
- Winding and lead arrangements respond differently to GlC SVC protection circuits have been readjusted on four induced core saturation as weH. For example. the current dis.
SVC's so as to render their operation reliable during tribution within parauel wind:ng paths and w magnetic storms similar work is being performed on the four remaming SVC's. leads depends upon the leakage flux paths and mutual cou-es w n ngs an a a may change sgh Energy, Mines and Resource Canada now provides Hy- cantly under GlC-induced saturation owing to the change in dro-Quebec with updated forecasts on the probabiHty magnetic field intensity, H, and the resultant changes m the of magnetic disturbances. These forecasts are used by boundary conditions for the leakage field path, the System Control Center dispatcher to position the transmission system within secure limits. Y
- ES IN STEEL MBERS A.C. voltage asymmetry is monitored at four key lo-cations on the system (Boucherville, Arnaud, LG2, The changes in the magnetic intensity, H, and the magnetic Chatgeaguay). Upon detection of a 3% voltage asym.
boundary conditions resulting from the GIC excitation bias metry at any one location, the system control center can increase the losses m steel plate, the losses for fields dispatcher is alarmed and willimmediately take action paraffel to the plane of the plate increase nearly as the square j
! to position system transfer levels within secure limits of H. Note also that the level of losses incrasse approxi- '
if this hasn't already been done because of forecasted mately as the square root of the frequency of H, owing to the magnetic activity. effect of depth of penetratson. The magnetic field along yoke clamps and leg plates in core form transformers and in Tee beams and tank plate in shou form transformers closely OPERATING LIMITS DURING matches the magnetic gradient in the core. Areas of the tank MACNETIC DISTURBANCES and core clamps are subjected to the winding leakage field. j (AND ALERT SITUATIONS) (f the core naturates, the magnetic field impressed upon the steel members may rise ten to one hundred times normal due The following operating IImits are now being applied: to the saturation and the effects of the leakage field. The 10% safety margin shall be applied on maximum trans- fosses in the steel members wul rise hundreds of times i
forlimrts mal. non under haN-wck satwah On W steel swfaces
- oddy loss density may rise ten to thirty watts per square inch.
! Maximurn transfer limits shall not take into account appr schingthe the thermal flux denarty of an electric range ele- ,
!
- availability of static compensators deemed unreliable, ment. l Adjust the loading on HVOC circuits to be within the !
j Surface temperatures rise rapidly with this thermal flux and 40% to 90%, or less, of the normal futiload rating.
18 can resutt in degradstion of insulation tovenmg the steel 1 t
i IEEE Power Engineering Review. October 1989 !
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. ATTACitMmT 3 l DeUtient v M r Design Deficiency manust UPS has Wendor no bat.ery manual f test maintenance circuit sectaon does not mention batteries.
Batteries have not MP COF Design Deficiency .ed ,s in f
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g cg g, y ~ niay ,
' I char ac t er ist-batteries treaker ses prevents ,
fastction
. AC g , 'l transfer to per desigra srput to . deg enverter Iogac power [
! tput.
54 ply is
'me a@nt enance preferred l
1 Gremd Voltase AC pouer to logic power logic trips fault occurs en transient logic modate greakers leads stoply on power pygS-UP51A 8, 25 S phase of main on stat 6en for UP$1A-0,G cutput supply- ~ C.D,G trip 08-f,CE.4 do not auto toss of ett i tr ansf ormer AC power empersences d
open;
- transfer to
- toads on 2
sisyt y voltage fassure. - maint. I the transtent goes tou . does
.ggagre,t UPS14 0*G gy.
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6 Fault Permissives is cleared e ibit C3-4
- i. in 6 cycles; g1 eater from I transfer ctosing
'coupleted in 12 cyctes
, f, CS-4 needed b' to transf maint.sig ,er gy to enverter i output jc
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ELECTRICAL DISTRIBUTION SYSTEM EVALUATION REPORT OF EVENT ON 8/13/91 - NMP2 l
l l
l PREPARED BY:
RWk c> lrfm ELECTRICAL DESIGN GROUP - UNIT 2 l
REVIEWED / CONCURRED BY:
& V- l4" 'l/rl?)
A.K. JULKAf SUPERVISOR' /-
ELECTRICAL DESIGN - UNIT 2 mm1 ^
[ ban ii
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TABLE OF CONTENTS I EVENT DESCRIPTION BACKGROUND l
INFORMATION AVAILABLE l
EVENT EVALUATION System Conditions / Disturbance-Oscillograph Relay Room Indications l -
Switchgear 2NPS-SWG001 and 003 Evaluation Main Generator Evaluation Plant Communication Fire Protection Systems Plant Essential Lighting System Group 9 Isolation Valves Closure Reactor Manual Control System Feedwater Control System Feedwater Pump Trip Annunciators and Computers CONCLUSION RECOMMENDATIONS ATTACHMENTS NSK2 -
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NMP2 ELECTRICAL DISTRIBUTION SYSTEM Event Description On August 13, 1991 at about 6:00 a.m., the NMP2 plant was running at full power and connected to the Scriba Substation 345 KV bus through line #23. The onsite normal power distribution system 13.8 KV buses, 2NPS-SWG001 and 003, were receiving power from the NSS transformer 2STX-XNS1. The onsite emergency distribution system 4.16 KV buses 2 ENS *SWG101, 102, 103 were receiving power l
from RSS transformers 2RTX-XSRIA and IB which were connected to Scriba substation through 345/115 KV transformers. When the plant was running at full power at about 6:00 a.m., the main step up transformer 2MTX-XM1B developed _ a fault and the appropriate protective relays sensed the abnormal conditions and activated their respective lockout relays. The lockout relays in turn initiated a main turbine trip and transferred normal power distribution loads from the NSS transformer to the RSS l transformers through fast transfer relaying. During the fast l transfer of power supplies to the normal distribution system, five (5) plant UPS's 2VBB-UPS1A, 1B, 1C, ID and 1G tripped and caused a power loss to plant computer systems, annunciation systems in main control room, communication systems, essential lighting and fire protection panels annunciation in the main control room.
Background
The NMP2 unit generator 2GMS-G1 is connected to the main generator step up transformers 2MTX-XM1A, 1B, and 1C which step up the generator voltage of 25 KV to 345 KV for interconnection to the NMPC grid at Scriba Substation via a 345 KV transmission line. The generator step up transformer consists of four shell i type oil immersed, single phase units. Three of these four transformers are connected to form a 3 phase 24.3 KV delta on the low voltage side and 3 phase 345 KV grounded Wye on the high voltage side. The fourth transformer is a spare unit.
The plant normal station service (NSS) transformer 2STX-XNS1 is also connected to the unit generator which steps down 25 KV i j
output of the generator to 13.8 KV for the plant normal power )
distribution system. The NSS transformer'is a 3 winding (split-secondary) transformer and feeds two 13.8 KV buses, 2NPS-SWG001 and 2NPS-SWG003, to supply power to plant nonsafety related-loads.
NSK2 2
O The two reserve station service (RSS) transformers 2RTX-XSR1A and 1B provide offsite power to the onsite power system. These RSS transformers step down the 115 KV offsite power to 13.8 KV and 4.16 KV for the plant normal and emergency power distribution systems respectively.
Under normal operating conditions, the plant onsite normal power distribution system is energized from the unit generator via the NSS transformer. In the case of a loss of the unit generator, the offsite power sources provide alternative power for the normal onsite power system through the RSS transformers. The onsite normal power distribution system 13.8 KV buses 2NPS-SWG001 l and 2NPS-SWG003 are normally energized from the NSS transformer 2STX-XNS1, In case of a loss of power from the normal source, these buses are automatically transferred to the offaite power sources via RSS transformers 2RTX-XSR1A and 2RTX-XSR1B respectively. This transfer can be accomplished in two modes; fast or slow. A single line representation of the above arrangement is shown in Attachment 1.
l The UPS system is divided into the emergency or safety related UPS system and the normal or non-safety related UPS system. The plant normal uninterruptible power supply (UPS) system provides power to the plant non-safety instrumentation and control loads, annunciators, computers, communication systems, fire protection panels, RPS system and essential lighting. The plant emergency UPS system provides power to plant safety related instrumentation l
and control systems. A single line representation of the plant UPS system is shown in Attachment 2.
The 75KVA normal UPS's affected during the event on 8/13/91 provide power to the plant normal instrumentation, controls, essential lighting, annunciators, computer loads, communication and Fire protection panels.
Protective Relayinc Description The main generator, main step up transformer and NSS transformer are protected by the following four protection schemes;
- 1) unit protection alternate 1,
- 2) unit protection alternate 2,
- 3) generator backup protection,
- 4) unit protection-backup.
NSK2 3
s This is illustrated in Attachment #3 in a single line diagram.
Protection schemes 1 and 2 above consist of high speed protective relays and the 3 &4 schemes use slow speed relays. Unit protection schemes 1 & 2 initiate a fast transfer of the switchgear buses 2NPS-SWG001 and 2NPS-SWG003 to the RSS source which occurs within 6 cycles after loss of normal power. If automatic fast transfer is not accomplished within 6 cycles, then the fast transfer is blocked and a slow transfer is initiated after a time delay to allow for decay of residual voltage on the deenergized buses and to shed selected motors from the power source to prevent excessive surges upon restart of the equipment.
This fast / slow transfer scheme is described in detail in USAR Section 8.3.1.1.2, Page 8.3-4.
Information Available The following data for the event was collected and is provided in Attachments 4 and 5.
- 2. NMP2 normal and emergency distribution system protective relaying status from control room records.
No other data is available because the NMP2 computer and annunciation systems were inoperable due to the loss of the normal UPS's. In addition, the control room oscillograph was found to be out of service at that time.
Event Evaluation The evaluation of various items during this event is provided as follows:
a) System Conditions / Disturbances-Oscilloaraoh The record of event and system conditions are recorded in the oscillograph chart obtained from Scriba substation which is provided in Attachment 4. This chart shows that NMP2 was operating at full power prior to the event on 8/13/91. At !
the initiation of the event, the chart indicates a decrease l in voltage on Phase 'B' of the 345 KV bus for approximately l 6 cycles after which the voltage returned to normal without any further visible transient behavior. During the same period, the current in one of the phases of the 345 KV line ,
connecting NMP2 and the Scriba Substation sharply increased '
to 3-4 times its prior value indicating a fault. After 6 cycles, the fault was cleared and line 23 (345 KV line to Scriba from the plant) was isolated. This confirms that the fault lasted only for about 6 cycles.
NSK2 4
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e The oscillograph chart for the Scriba Station 115 KV Bus reveals that during the fault duration of 6 cycles, the 115 KV bus voltage dropped. After the 345 KV line #23 was isolated, the 115 KV bus voltage returned to normal. The oscillograph chart for the 115 KV bus confirms that the fast transfer of the NSS transformer loads to the RSS transformer 1 occurred after about 6 cycles from clearance of the fault I and is in accordance with USAR Section 8.3.1.1.2.
The oscillograph charts for the 115 KV and 345 KV buses do not show any disturbances before occurrence of the fault and l after clearance of the fault. !
b) Relav Room Indications The relays that actuated during the event are shown on the abbreviated single line in Attachment 3. A review of the relay data indicates that the main transformer ,
differential relay actuated.to isolate the fault in the !
transformer. Initiation of this relay actuates lockout I relays of the unit protection schemes, initiates a turbine trip and fast transfer of the NSS transformer loads to RSS transformers. In addition to the main transformer differential relay, the unit differential ,
relay also actuated, which initiated a turbine trip and l fast transfer. Generator protection and unit protection backup relays also actuated. The fast transfer occurred before these backup protection schemes could block the fast transfer.
During the transfer of the normal power distribution !
system from the normal source to its alternate source, l the flags on the degraded voltage relays of the Class 1 1E power distribution system came in, but there was no indication of offsite power breaker tripping and diesel generator starting. The degraded voltage condition appears to have occurred only during the duration of the fault as evidenced by the Scriba substation oscillograph chart for the 115 KV buses. Since the l l degraded voltage trips are time delayed without loss of coolant accident (LOCA), the diesel generators signal i
was not initiated and the offsite breakers did not
- trip. The degraded voltage scheme, therefore, functioned as designed and agreed with USAR commitment.
l This degraded voltage scheme is discussed in USAR Section 8.2.2, Page 8.2-24C.
NSK2
e c) Switchaear 2NPS-SWG001 and 003 Evaluation The 13.8 KV switchgear 2NPS-SWG001 and 003 receive their normal power from the NSS transformer. In the case of a loss of power from its normal source, the power supply to these switchgear buses is automatically transferred to the RSS transformers. The relay actuation and Scriba oscillograph chart indicate that the fast transfer occurred the way it was designed and as described in USAR Section 8.3.1.1.2, Page 8.3-4 for both the switchgear buses.
Further investigation of the event by NMPC operation revealed that the circuit breakers feeding 13.8 KV reactor feedwater pumps and condensate booster pump j fed from switchgear 2NPS-SWG001 were tripped. A detailed review of automatic transfer scheme was performed to determine if these large motors were tripped due to this transfer scheme. The automatic transfer scheme is designed such.that the large motors trip before slow transfer to avoid residual voltage.
l The review of the Scriba Substation 115 KV oscillograph chart clearly confirms that fast transfer scheme worked and loads were picked up by the 115 KV reserve power sources. A further review of the feedwater system revealed that the loss of power supply from the normal UPS's caused the opening of minimum flow valves which-in turn triggered tripping of the feedwater pumps and I condensate booster pump. See Section 'L' for further l
analysis of this occurrence. ,
1 d) Main Generator and Other Related Eculement Evaluation
'( The fault on the main step up transformer was detected by protective relaying which tripped the main turbine / generator which in turn initiated an automatic scram of the reactor. The fault on the main transformer was on the 345 KV winding which is wye I
connected. The fault on the secondary side was j transferred to the low voltage side windings. The low i voltage side winding was damaged. The main l generator / turbine was tripped by unit protection ;
alternate 1 and 2 lockout relays within about 6 cycles i from the event as is evidenced by the 345 KV line oscillograph chart. The generator may have been coasting for some time with residual excitation and
. supplying fault current to the 25 KV system after the trip. This current is small compared to the initial l fault current on the secondary side due to main l transformer impedance. This small fault current may L- NSK2 6
I e
not have any significant effect on the main generator thermal capability but it is recommended to megger main generator and check surge arrestors prior to startup.
In addition, as recommended in Attachment 10 by General Electric, the generator manufacturer, a thorough inspection of the generator and its component should be performed. It is recommended that this inspection be performed during the next refueling outage.
It is also recommended that the unfaulted transformer units be meggered and dobled in accordance with i
manufacturer's recommendation. The generator and l associated equipment have been tested and details are included in the transformer report.
e) Plant Communication Systems NMP2 plant communication systems consist of the following:
- 1) Dial Telephone System A dial telephone system provides communication between selected office areas and selected locations inside and outside the station. The dial telephone system is connected to the NMPC ;
telephone tie system for offsite communication. !
The telephone system main equipment receives its l power from the plant normal UPS system.
- 2) Radio Communication Systems A hand held portable radio communication system _is provided for communication between station personnel within the plant. This system utilizes a leaky wire antenna system which are fed from the plant normal UPS system.
- 3) Pace Partv/Public Address System A PP/PA system with five party channels and one page channel is provided for communication for various station buildings and locations. The system is powered from the plant normal UPS system.
- 4) Maintenance and Calibration Communication System An M/CC is provided for voice communication in areas requiring communication for testing, NSK2 7
naintenance, etc. It is powered from the plant normal 120V AC power system.
- 5) Sound Powered Communication System An SPC is provided for voice communication in case of total loss of electric power to PP/PA and M/CC systems. This system requires no plant electrical power.
Event Evaluation Three of the five communication systems require plant UPS systems to function. Due to loss of normal UPS systems during the event, the three communication systems, dial telephone system, radio communication system, and page party /public address system, were lost. The only communication systems available were the maintenance and calibration communication-system and the sound powered communication system which is mostly used for testing and maintenance activities.
Even though the PP/PA system is grouped in two separate independent paging systems with three UPS systems to provide redundant paths of communication throughout the plant, the communication systems were lost due to the multiple failures of the normal UPS system. The existing communication system design with redundant paths of communication throughout the plant using three normal UPS's is adequate; the root cause of the multiple failure of the normal UPS's will be determined / evaluated and appropriate corrective action taken if required to ensure that multiple normal UPS failure will not reoccur. The plant communication system is described in USAR Section 9.5.2.
f) Fire Protection System NMP2 Fire Protection and Detection systems are fed through the two stub buses 2NNS-SWG016 and 015 through an automatic transfer switch. The primary source which feeds the two stub buses is the unit generator 2GMS-G1 through the normal station service transformer 2STX-XNS1. In the event of unit trip, these stub buses are transferred to the offsite power sources through a fast or slow transfer of 13.8 KV buses 2NPS-SWG001 and 003 respectively. In the case of loss of offsite power, these stub buses are connectable to emergency diesel generators if there is no LOCA.
l l
NSK2 8
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l NMP2 has two fire pumps, one diesel driven and one
, motor driven. The motor driven fire pump is powered l from 4.16 KV non-safety related bus 2NPS-SWG012.
Further information on this system is provided in USAR Appendix 9A.
l The Unit 2 fire detection system is fed through the two stub bases through an automatic transfer switch. The primary source which feeds the two stub buses is the i unit generator, and the secondary sources include either of the two offsite power sources, or the diesel generators. In case of the loss of the primary source, the transfer switch automatically connects the system to the secondary source. This arrangement satisfies the intent of the requirements of NFPA 72D, Section 2220. This fire detection system is described in USAR Section 9A.3.6.1.6, Page 9A.3-49.
A listing of fire panels installed in NMP2 is provided on the following.pages. Each panel powered from AC is provided with a primary and backup power source. In
- the event of momentary loss of both primary and backup, l the system is provided with an internal battery power l supply except for 2 CEC-PNL849, 2FPM-PNL200 and 201.
l These are powered from normal UPS 2VBB-UPS1G. 2 CEC-PNL849 provides main control room alarm for fire in any area in the plant; 2FPM-PNL200 and 201 are fire protection computer panels. This level of detail is not provided in the USAR.
Status of Fire Panels The status of fire panels during the event is shown in i Attachment 6. As indicated in Attachment 6, 2FPM-PNL l
- 200 and 201 were lost when the UPS was lost. In j addition, 2 CEC-PNL849, which is fed from the normal UPS l System, was also lost causing the loss of annunciation in the main control room for fire protection systems.
The status of fire panels reported above, is in l
accordance with the existing fire panel design.
Event Evaluation As reported in Attachment 6, of the 20 fire panels at
, Unit 2 only two (2) transferred to internal battery l back-up_during this event. This transfer is in ,
l accordance with the local fire panel design. While on '
battery power, because the normal AC was still available, functions of these two panels were still available.
NSK2 9
' i As indicated in Attachment 6, some panels provided local trouble alarms and it is due to the fact that their supervisory control circuits detected a momentary dip in the normal AC power supply as they are designed to do so. This level of detail is not provided in the USAR.
During this event plant-communication was not i
available. However, as stated in Attachment 6,_ fire l brigade started its roving patrol soon after the i failure of the transformer and they have used had held portable radios with Channel 10, which is their normal practice during the loss of communication-systems.
During this event, control room did not have the capability to monitor various fire panel annunciations.
However, fire suppression / indication could have been initiated locally. In addition fire suppression capabilities existed from.the~ control room, because the control circuits in control room are powered from local i panels.
In addition, it'is concluded that this event did not
! involve any 10CFR 50 Appendix "R" concerns because the e event is not associated with any exposure fire.
j Fire Protection and Detection Panels and Their Power Supplies The NMP2 plant fire protection panels and their power supplies are as follows:
Component ID Power Source 2FPF-PNL136 2SCA-PNL500 2 SCI-PNLA102 2FPL-PNL176 2BYS-PNLA101 (DC Power) 2BYS-PNLB101 (DC Power) 2FPL-PNL176-1 2BYS-PNLA101 ~ (DC Power) 2FPL-PNL176-2~ ' 2BYS-PNLA101 ~ (DC - Power) 2FPL-PNL177 2BYS-PNLA101 (DC Power) 2BYS-PNLB101 (DC Power) 2FPL-PNL177-l' 2BYS-PNLA101 (DC Power) 2 FPL-PNL177-2 2BYS-PNLA101 (DC Power).
2FPL-PNL230 2BYS-PNLA101 (DC Power)
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Component ID Power Source i 2FPL-PNL231 2BYS-PNLA101 (DC Power) 2FPL-PNL273 2BYS-PNLA101 (DC Power) l
! 2FPM-PNL101 2SCA-PNL500 2SCA-PNL600
l 2FPM-PNL104 2SCA-PNL600 l 2SCA-PNL500 2FPM-PNL105 2SCA-PNL600 2SCA-PNL500 2FPM-PNL106 2SCA-PNL600
, 2SCA-PNL500 i
l 2FPM-PNL107 2SCA-PNL600 l 2SCA-PNL500 l 2FPM-PNL108 2SCA-PNL600 l
2SCA-PNL500 2FPM-PNL113 2SCA-PNL500 2SCA-PNL600 2FPM-PNL114 2SCA-PNL500 2SCA-PNL600 2FPM-PNL117 2SCA-PNL500 2SCA-PNL600 2FPM-PNL119 2SCA-PNL600 2SCA-PNL500 2FPM-PNL120 2SCA-PNL600 2SCA-PNL500 2FPM-PNL121 2SCA-PNL500 2SCA-PNL600 2FPM-PNL123 2SCA-PNL500 t' 2SCA-PNL600 NSK2 11
4 l
Component ID Power Sonrce 2FPM-PNL125 2SCA-PNL500 2SCA-PNL600 2FPM-PNL126 2SCA-PNL500 2SCA-PNL600 2FPM-PNL127 2SCA-PNL500 2SCA-PNL600 2FPM-PNL128 2SCA-PNL500 2SCA-PNL600 l 2FPM-PNL129 2SCA-PNL600 2SCA-PNL500 2FPM-PNL131 2SCA-PNL500
- 2SCA-PNL600 2FPM-PNL132 2SCA-PNL600 2SCA-PNL500 2FPM-PNL200 2VBB-UPS1G >
2FPM-PNL201 2VBB-UPS1G 2FPM-PNL233 2SCA-PNL102 2SCA-PNL600 -
g) Plant Lichtina Systems !
NMP2 station lighting consists of the following: j 1
- 1) Normal Lighting System
- 2) Emergency Lighting System 1
- 3) Essential Lighting System
\~ l 1
-4) Egress Lighting System j
- 5) 8-Hour Battery-Pack Lighting System NSK2 12 i
_...-L---__--_-_------- . . , - - ._, ..,.n ,, g-n ,n., ,
I
~ l The normal lighting system provides adequate )
illumination in all areas of the station under normal operating conditions. The emergency lighting system provides adequate illumination in areas required for 4 operating the safety-related equipment during emergency conditions. The essential lighting system provides partial illumination for certain critical areas of the station requiring continuous lighting such as the control room and for passageways to and from areas where safety-related equipment is located. The egress lighting system provides adequate illumination for all egress signs and egress routes inside the plant. The 8-hour battery pack lighting provides illumination in all areas required for operation of safe shutdown equipment and in access and egress routes thereto in !
case of exposure fire. The above discussion of the l plant lighting systems are consistent with USAR Section l 9.5.3.
The normal lighting system is powered from the plant i normal power distribution system except reactor I building normal lighting, the emergency lighting system is powered from the plant emergency power distribution I system, the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting system is powered by their own battery.
The Reactor Building normal lighting receives power from offsite source in a way similar to the emergency lighting system. The normal reactor building lighting is tripped from the Class 1E bus by an accident signal and is blocked from closing as long as the accident signal is present. The Reactor Building normal lighting is also tripped upon sustained undervoltage on the load center from where it receives power.
The essential lighting system receives power from station normal UPS system 2VBB-UPS 1B, 1C and 1D. A single line representation of the power supplies involved with the UPS is provided in Attachment 2 and the critical areas of the plant provided with essential lighting is shown in Attachment 7. The plant egress lighting also receives power from the plant normal UPS panels 2VBB-UPS 1B, 1C and 1D. This is in accordance with USAR Section 9.5.3, Page 9.5-20.
Status of Essential and Earess Lichtina During the event on August 13, 1991, power supplies from normal UPS panels 2VBB-UPS 1B, 1C and 1D were not available. All areas of the plant that are provided with essential and egress lighting, loss of partial illumination NSK2 13
l l
l resulted until such time the power to these UPS's was ;
restored. However, one or more of the other lighting systems namely, emergency, normal and 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack were available in these areas during this event.
The stairwells are provided with essential lighting only except where 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting is added for Appendix R compliance. Illumination to these stairwells was not available due to loss of normal UPS.
The 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting did not energize because there was no loss of normal power.
Event Evaluation The root cause of loss of power from normal UPS is evaluated separately in another report. During the event, some areas of the plant lost partial illuminations provided by essential lighting for sometime. Areas critical for safe shutdown where this lighting are identified are provided in Attachment 7.
During this event the plant was safely shutdown from the control room. Because the control room is provided with adequate lighting without the essential lighting, loss of essential lighting did not adversely affect the operator actions needed to bring the plant to safe shutdown.
The access route used by the operators during this event for restoration of the normal UPS power (Attachment 8) supplies was illuminated from normal lighting except for the stairwell where portable handheld lights were used. (FSAR Sec. 9.5.3.3 allows the use of portable lighting in the form of handheld flashlights for short excursions into the plant). The normal UPS locations were illuminated by normal lighting. Therefore, restoration of UPS power was unaffected by loss of essential lighting. Even though the essential and egress lighting are powered by three normal UPS's, during this event due to multiple failures of all normal UPS's, essential and egress lighting systems were not available. The existing essential and egress lighting design is adequate, however, the root cause of the multiple failures of the normal UPS's will be determined / evaluated and appropriate corrective action taken if required to ensure that multiple normal UPS's failure will not reoccur.
The proposed plant modification 89-042 will enhance the reliability of stairwell lighting where 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery l pack lighting is provided. l l
NSK2 14 )
l l
I
1 I
l Status of Normal Reactor Buildina Lichtina During the event on August 13, 1991, it was reported by the operators in the reactor building that some areas of the reactor building lost lighting momentarily.
Event Evaluation Normal lighting for reactor building general areas, work areas and electrical equipment areas is provided with low wattage high pressure sodium vapor lights. In the event of power interruptions or voltage dip lasting for more than one cycle, these fixtures extinguish and do not restart until the lamp cools and pressure decreases. When a power supply to continuously energized sodium vapor light is interrupted, it has a cooldown period before a restrike of the lighting-can occur. The cooldown period depends upon the rating of the light bulbs. During the event, the emergency distribution system experienced a transient due to the fault on the Phase B main transformer. During the event, the Reactor Building normal lighting in certain areas where these high pressure sodium vapor fixtures are provided, was interrupted for approximately 30 seconds. This momentary loss of lighting was due to the inherent design of low wattage high pressure sodium vapor lighting which requires cooldown period prior to restrike whenever power is interrupted. The same scenario could occur in the plant wherever power supply to high pressure sodium vapor fixture is interrupted momentarily, however, there is no indication of such a loss in other areas of the plant. Therefore, it is consistent with NMP2 lighting design and USAR Section i
9.5.3. I h) Groun 9 Isolation Valves Closure The group 9 primary containment isolation valves are part of containment purge system. These valves are !
listed in Technical Specification Table 3.6.3-1, Page l 3/4 6-24 and USAR Table 6.2.56, Page 11 of 24. The ,
function of group 9 isolation valves is to limit the i potential release of radioactive materials from primary I containment. These isolation valves are opened during '
power operation only at infrequent intervals to allow injection of nitrogen into primary containment to inert or de-inert the primary containment at a desired pressure.. These valves, if open, receive signal to close if any of the following happen:
NSK2 15 l
I t
a) High radiation through standby gas treatment system (SGTS). The SGTS radiation monitor located in the main stack is designed to continuously monitor offsite release and provide isolation signals to these isolation valves.
l b) High drywell pressure.
c) Reactor low water level.
d) Manual isolation of main steam isolation valves.
Event Evaluation During this event, the group 9 primary containment isolation valves closed. This isolation is the safe mode of operation limiting potential releases of radioactive material from primary containment.
The initiating condition for these valves occurred as a result of loss of power to radiation monitor 2GTS-RE105 when UPS power to the DRMS computer was interrupted.
The actual isolation occurred when the logic was reenergized upon restoration of the UPS power supply to the monitor's auxiliary relay circuit. Therefore, group 9 isolation valves closed as designed and is consistent with USAR Section 6.2.5.2.4, Page 6.2-77.
j) Reactor Manual Control System The reactor manual control system (RMCS) provides the operator with means to make changes in nuclear reactivity via the manipulation of control rods so that reactor power level and core power distribution can be controlled. This system is a power generation system and is not classified as safety related. The RMCS receives electrical power from the 120 V'AC normal UPS.
The RMCS does not include any of the circuitry or devices used to automatically or manually scram the reactor. The RMCS control and position indication circuitry is not required for any plant safety function nor is it required to operate during any associated DBA or transient occurrence. The reactor manual control circuitry is required to operate only in the normal plant environment during normal power generation operations. The discussion of RMCS is consistent with USAR Sections 7.7.1.1, Pages 7.7-1, 2, 14.
J NSK2 16
l l
Event Analysis The RMCS was lost during this event because its power source, the normal nonsafety related UPS, was lost.
The loss of RMCS is not a concern during this event.
Since the plant was automatically scrammed during this event, the RMCS need not perform any function after the scram. This RMCS is used by operator only during normal plant operations. Therefore, if the plant had not automatically scrammed during the event, loss of RMCS would not have caused a safety concern based upon )
the following:
- 1) EOP's provide guidance to the operator under situations involving failure to scram, and
Although this system was lost during this event, its importance diminished once the automatic scram occurred. Therefore it is concluded that the RMCS function was consistent with USAR Section 7.7.1.1.
k) Feedwater Control System The feedwater control system controls the flow of feedwater into the reactor vessel to maintain the vessel water level within predetermined limits during all normal plant operating modes. During normal plant operation, the feedwater control system automatically regulates feedwater flow into the reactor vessel. The system can be manually operated. The feedwater flow control instrumentation measures the water level in the i reactor vessel, the feedwater flow rate into the l reactor vessel and the steam flow rate from the reactor !
vessel. During automatic operation, these three ,
measurements are used for controlling feedwater flow.
The feedwater control system receives its normal power supply from the normal UPS. The feedwater control system is designed to lock in its last position upon a loss of power to its control electronics. The feedwater control system is discussed in USAR Section 7.7.1.3, Page 7.7-23.
Event Analysis During this event, upon loss of the normal UPS's, the feedwater control system performed as designed and failed in its last position. Therefore, it is concluded that the feedwater control system function was consistent with USAR Section 7.7.1.3.
NSK2 17
i i*
- 1) Feedwater Pumo Trin:
Feedwater is provided to the Reactor Pressure Vessel (RPV) via the Condensate Pumps, Condensate Booster Pumps and the Reactor Feed Pumps shown in Attachment 9.
The Condensate Pump draws condensate water from the Condenser and provides the necessary Net Positive Suction Head (NPSH) for the Booster Pumps. The Condensate Booster Pumps provide the necessary NPSH for the Reactor Feed Pumps. A minimum flow control header is provided off the discharge header of each pump to ensure that the minimum flow is maintained through the associated pump. The minimum flow control valves and associated instrumentation actuates to maintain this minimum flow. The main feedwater control valves (LV10), located on the discharge header of the Reactor Feed Pumps, modulate to control reactor water level.
The feedwater control system is powered by normal UPS power supplies. The above discussion is consistent with USAR Section 10.4.7.
Event Evaluation l
It was reported during this event that feedwater pumps tripped. An evaluation of this condition reveals that reported happenings are consistent with the system as l designed and is in consistence with USAR Section 10.4.7. The instrumentation controlling the minimum flow recirculation valves on the condensate, condensate l
booster and the feedwater pumps is powered from the normal UPS's. These instruments are also designed to open the valve upon loss of power in order to protect the pumps. Upon loss of normal UPS, the feedwater control valves fail locked in their last position.
Following the turbine trip, an ATWS signal would attempt to drive the feedwater control valves closed, however since an ATWS signal was not present, this did not occur. With the feedwater control valves failed locked and the minimum flow control valves (FV2) driven full open, feedwater flow increases and approaches pump run-out. The Reactor Feed Pump NPSH decreases to the low-low pressure trip point, tripping the Feedwater Pumps. The Feedwater pump control circuit does not utilize an auto transfer logic to standby Feedwater Pump; therefore, feedwater flow is lost. The instrumentation circuits for all other minimum flow
' control valves are also powered by normal UPS power supplies. These valves all fail in the open position with the loss of UPS and contribute to the loss of Feedwater pump and condensate booster pump. This is consistent with USAR Section 10.4.7. I NSK2 l 1
18 l
l l
m) Annunciators and Computers The plant annunciator system provides information to I the plant operators by windows located on the main operator panelboards and on back panels within the Power Generation Control Complex (PGCC). This system does not include annunciators on local panels throughout the plant and on special panels, e.g., fire protection, within the PGCC. The plant annunciator system is non-safety related and is connected to the normal power distribution system through normal UPS's. The plant annunciator system is not discussed in the USAR.
Several computer displays, with inter-active keyboards, ,
are located in the PGCC. These displays are from the )
following computer systems. '
1 PMS -
Plant Process Computer LWS -
Liquid Radwaste Computer, which has the ,
following subsystems: I i
LWS - Liquid Radwaste Control {
l GENTEMP - Generator Temperature Monitoring ERF - Emergency Parameter Display System SPDS - Safety Parameter Display System DRMS -
Digital Radiation Monitoring System 3D Monicore - A system used primarily for. core calculations and monitoring In addition, noble gas information is provided to the i plant operators from the GEMS (Gaseous Effluent Monitoring System) computer by chart recorders on a back panel; and the operators have access to the GETARS (General Electric Transient Analysis & Recording System) computer.
All of the above computer systems are non-safety related and are connected to the normal power i distribution systems through normal UPS's. There are l some safety related radiation monitoring skids that provide input to the DRMS computer. However, these skids also provide safety related indication in the PGCC that is independent of the DRMS computer.
NSK2 19 l
l
The Plant Process Computer is discussed in Section 7.7.1.6 of the USAR, where it is mentioned that the computer is non-safety related. l l
USAR Section 11.2.1.2 covers the Liquid Radwaste System l design basis and states that the power supply for all
! Radwaste System components is provided from non-Class ]
l 1E power sources. This is compatible with the Safety l Parameter Display requirements since NUREG-0737, i Supplement 1 states that the SPDS need not be qualified to Class 1E requirements.
The process and effluent radiological monitoring and l sampling systems, which include the DRMS and GEMS l
computers, are discussed'in USAR Section 11.5. This section defines which monitors are safety related and which are non-safety related. The DRMS and GEMS design complies with this USAR section.
Area radiation and airborne radioactivity monitoring instrumentation, which include the DRMS and GEMS computers, are discussed in USAR Section 12.3.4.1.
This section defines which monitors are safety related and which are non-safety related. The DRMS and GEMS
! design complies with this USAR section.
A description of the 3D Monicore computer system was added to USAR Section 7.7.1.6 by LDCN U-1235. This LDCN states that the 3D Monicore system is non-safety related.
The designation of the computer systems mentioned above l as non-safety related is consistent-with the explanation of the Uninterruptible Power Supply System in USAR Section 8.3.1.1.2. In this section it is stated that 2VBB-UPS1A feeds the radwaste computer l
hardware, 2VBB-UPS1B feeds local non-safety related l
radiation monitoring microprocessors, and 2VBB-UPS1G feeds plant computer loads.
! Event Evaluation With the loss of the normal UPS's, the plant annunciation system and the computer systems listed above became inoperative due to the loss of power.
This is consistent with the plant design and the description of the plant in the USAR. These systems are non-safety related and, hence, are not required to shut down the plant following a design basis event.
l NSK2 l 20 l
l l
)
CONCLUSION Based on the above evaluation, it can be concluded that the plant responses during the event on 8/13/91 is consistent with USAR descriptions.
RECOMMENDATIONS Based on the above evaluation, the following long term recommendations are provided.
1l Plant Oscillograph - The in-plant oscillograph should be replaced with a more reliable and functional unit.
If this oscillograph was functional during the event on 8/13/91, adequate data _could have been available to accurately evaluate the cause of the disturbance.
- 2) Essential Lighting - The proposed modification 89-042 should be implemented as soon as possible to enhance the reliability of stairwell lighting where 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> battery pack lighting is provided.
- 3) Ccotrol Power Supplies - During the Electrical Distribution System evaluation, it was revealed that most of the systems important to plant operations such as feedwater system, annunciation system, etc, receive their control power from either normal UPS 1A, 1B or both. It is recommended that control power supplies
, for these systems be evaluated and reconfigured to I
avoid plant transient due to loss of single normal UPS.
- 4) Main Generator - It is recommended that a thorough visual inspection be performed of the generator stator l and winding support system during the next refueling I outage (see Attachment 10).
l NSK2 21
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pTAcHmeNTS Pace ~2WS LIST OF PROTECTIVE RELAY ACTUATED QN AUGUST.13, 1991 Unit Protection Alt 1 Protective Relav Lockout Relav Action Ref. Dwa.
87-2SPMX01
- 86-1-2SPUX01
- Initiate Turbine Trip ESK-8SPUO1 Main Transformer 86-2-2SPUXO2
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Protective Relay Lockout Relav Action Ref. Dwa.
87-2SPUYO2
- 86-1-2SPUYO1
- Initiate Turbine Trip ESK-8SPUO1 Unit Differential 86-2-2SPUYO1
- Initiate Fast Transfer ESK-8SPUO3 Protection Relay to Reserve Station ESK-5NPS13 Transformer -
ESK-5NPS14 63-2SPMY01
- 86-1-2SPUY01
- Initiate Turbine Trip ESK-8SPUO3 Fault Pressure 86-2-2SPUY01
- Initiate Fast Transfer Sh.-2 Transformer to Reserve Station ESK-8SPUO3 Transformer Sh. 1 ESK-5NPS13 ESK-5NPS14 Unit Protection Backup I
l Protective Relav Lockout Relav Action Ref. Dwa.
l 50/51N
- 86-1-2SPUZ01
- Initiate Turbine Trip ESK-8SPUO4 i 2SPMZ01 86-2-2SPUZO1
- Initiate Slow Transfer ESK-5NPS13 l
Protection Relay After 30 Sec. ESK-5NPS14 Block Fast Transfer After 6 Cycles Generator Protection Protective Relav Lockout Relal Action Ref. Dwa.
Gen. Phase OC During 86-1-2SPGZO1
- Initiate Turbine Trip ESK-8SPG01 Startup 86-3-2SPGZ01
- Initiate Slow Transfer ESK-8SPG04 50-2SPGZO2 After 30 Sec. ESK-5NPS13 Block Fast Transfer ESK-5NPS14
- This Relay Picks Up Only When Unit is Off Line
]
l NSK1
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ATTJC BiENT 3 PAGE 3 of 3 -
Degraded Voltage Switchaear Lockout Relav Action- Ref. Dwa.
2 ENS *SWG103 27BA-2ENSB24 No Action Took Place ESK-5 ENS 18 27BB-2ENSB24 Degraded Voltage Stays ESK-8 ENS 02 27BC-2ENSB24 'During Fault Conditions 2 ENS *SWG101 27BA-2ENSA24 No Action Took Place ESK-5 ENS 14 27BB-2ENSA24 . Degraded Voltage Stays. ESK-BENS 01 27BC-2ENSA24 During Fault Conditions .
2 ENS *SWG102 27BA-2ENSC08 No Action Took Place 807E183TY.
27BB-2ENSC08 Degraded Voltage Stays Sh. 7 27BC-2ENSC08 During Fault Conditions ,
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- TO UPS DURINO FAULTED CONDITION f
4 FAULTED 345Kv CONDITION I o a t ! f . . . j 5 /s b 180kV iso I ww -- 2MTX-XM1A. B. C N 232KV , 21.55u 2 .bf mm 2 3 [ 82.5Kv 2' altKV L t o . 2 S ~23 KV I a a i n2 24.9/ ww TM A2STX XNSI @ j m j v 13.8KV 7.5'/. 16kV N 8 AV! .
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FROM A. R.- bb DitfMCf Nine Mile Point Nuclear station Distr 15 August 91 FILE CODE TO DATE x R smEcf Nine Mile Point Fire Protection Awvg.a Post Event Interviews After interviews conducted today with Fire Chief Bernie : Harvey, and Firemen Pat Brennan and Nark Locurcio, and concurrence with Terry Verallysa, System Expert Fire Detection and John Pavlicko of Caution Equipment Inc., I have reached the following, conclusions.
- 1. of the 20 fire panels at Unit 2, is maintained a normal power supply.
l 2a. Two fire panels LFCP113 and 123 transferred to internal battery backup. I 2b. These two panels while on battery will still function normally as long as the 120 VAC is available in the LFCP, which it was. There was no-interruption or doorease of fire protection / detection / suppression at the local fire panels. Fire Panels 849 and 200/1 being fed from UPS did have a power interruption. This would have left the control switches operable at Panel 849, (as they are fed from LFCP), but control Room with 4 no fire annunciation. Any fire suppression / indication could also have been initiated locally. ARA:dic Distribution T. Tomlinson A. Julka (FAX 7225 - SM) D. Pringle
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~T Nine Mile Point, Unit 2 l susJact Fire Protection Program i
4 Post Event 9/13/91 Interviews \ j Pire Dept. Personnel Interviews, Post Event of August 12, 1991 5 { Bernie Marvey - Chief - In early for coverage , interviewed for loss l cf power in Centrol Building. Lights blinked, loud noise (louder than ever heard in plant) , was in Fire Dept. office, told shift to { j get out into plant. Pat Wilson was in Rx Bldq, switched radios to Channel 10, standard , j Fire Dept. practice if suspect loss of repeator. I Pat Brennan was in the Foam Room and proceeded to the Chief's desk. 1 j Chief Harvey heard fire panel alarming when he got to Control
- Building. Want past Fire Panel 114 in Turbine Building passageway, i no audible alarms, seemed normal.
l Mark Locuroie went to Panel 126 - 214 elev. while chief Narvey went to Panel 127 - 244 elev. ; these were sounding trouble alara and DAX j was clear. Want past Panels 120, 121, 128; they were normal - no < audible. I l Prior to Site Area Emergency (SAE) message and evacuation being j announced - Pat Brennan reported Panels R.B. normal, called on l Gaitronics - had to silanos Panels 113 on T.B. 250 and then
- silenced all Panels in R.B., Panels 101, 103, 104, 105, 106, 107
- and lot.
j chief Harvey was going to trip systems wet in R.B, and. have man in
- R.S. Guards Lynn Root, accompanied by Larry ochener, called his supervisor, when _they saw transformer blow.
j Chief Marvey would have liked to get to transformer quicker for , i fire evaluation. He feels it was at least one hour before ,/ evaluation. chief Harvey feels Fire Dept. should have been part of initial j investigation / inspection team with operations. j a E i .
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- Aug. 13, 1991 Interview (Cont'd)
Pat Pat was in Foam Room approximately 0550, heard Lighting loud noise, went diassed, one to 1 l chief's office and asked what noise was. string of lights off (NOTE: these feed from Emergency - UPS should 4 have gone off) J Then he went on rover - heard alarms
- which were on water j
treatment system panel, then went to Panel 123. There were no Power lights j displays on DAX panel, was blank no lights were on. were off. Trouble light blinking. i i Want to T.B. 251 NW, signed sheet, stairtower dark 1(no problem, j knew way around), Turbine Track Bay dimly lighted. y j Went to T.B.-306 - OK, signed sheet i
" " T.B. Swgr 377 - CK, signed. sheet
" " T.B. 250 by Feedpumps - noted not running i
I
" by Panel 113 - no lights on, no audible or trouble alarm i estimates time approximately 0605 l Continued rover rounds to Panel 106 - South Stairtower R.B. 289 was alarming display said "on internal clock"
- had two troubles displayed j
Want to R.E. 215 - Fire panel 103 alazzing - silenced j
" " R.B. 1st - Fire panel 101 alarming - silenced i
both panels were in trouble - unknown i " " R.S. 175 - Signed sheet
" " R.B. 261 - SEGTS - CK Panel 105 - silenced troubles a
" " CO2 Room, about this time, evacuation alarm sounded went l to Unit 2 Control Room assembly point lt l Walked around with Pat Brennan on 8-15-91 to Panal 123 and Panel i 113, power on light was burned out on Panel 123. " Power on" light-was on, on Panel 113.
4 5 i i i 4 3 4
AUG 15 '9& 15 da ret ICT r1GMT & Cortl DTS P.5 kTh&#T (, ! PbG 6. +op4 Poet y Aug. 13, 1991 Interview (Cont'd) Mark Leemasie (called at home) Was located in the Fire Dept. Office when lights flickered and noise was heard. Radio communication was gone. Hear Mere was out. chief Narvey directed personnel to cover vital areas. Pat Wilson was in RX Bldg. Pat Brennan was roving T.B. Bernie & Mark were to cover control 31dg. Trip to c.B. uneventful Panels Passed in routes Panel 114 Elect. Say Elv. 261' Normal Panel 120 C.B. Elv. 2618 Norinal Panel 125 C.B. Elv. 261' Normal . Panel 121 C.B. Elv. 261' Normal Panel 125 C.B. Elv. 261' Normal Panel 127 C.E. Elv. 244' Trouble Morn sounding - Silenced Panel 126 C.B. Elv. 214' Trouble Horn sounding = silenced, also an amber , 1 light was lit on panel Checked valve room on C.B. elv. 214' light was on in room. No indication of system actuation. stairwells were dark, Elv. 261' C.B. was dark. S.A.E. announcement-and reported to control Room.
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I p11AcumEH7 7 PAGE J *f 9 88F2 LIGHTING SYSTEM POWER S0lEl af4) MINIMIN ILLUMENATION AVAllaeLE Pa0E 7 , MODES (F (PERATION ' 9(lRMAL LOCA TRaNStENT LOCA & SEISMIC . E Of-w Tw 'r 1 0F gg POWER um MIDL AMIL. POWER tLLUN. "I"* AMR. 1 0F LW MtN. - 1 gg 0F Mpl % OF gg MIN. ESSDITimL PRUviDEO PRovtDED POWER AVAll. SOURCES B7 POWER rFOOT m BY POWER 8F007 SOURCES PROVIDED NT POWER SWRTS PRDv!OED "'"E-* FOOr PUWER Ems PRUvt0ED "" L* lI0HII"U StamCE CMOLD S0WCE CA80LD B7 POWER S0WCE CANOLD BY POWER CaNI]LD BY POWER NI EN ' RE944RR$ SOURCE gggggg CWOLO IIL 800RM L YES NORMAL NONE* N0pp4mL MTOR m NO NORMAL NO NORMmL YES EL. 215 2 WEB 4 PS!C EE-67C ESSENTIAL YES ESSENTlal YES ESSEurial NO ESSEurtal YES ESSEMital YES sPDsi FUEL e HOW g e MoUR 8 HOUR pc gar.Paca ent. Pack YES YES 8 HOW G MOUR ent. Pack ent.Pacw YES 880NE ent.Pacw
- NORMmL 'YES WORMmL NONE* NORMAL NO 880RMfL peg NORMAL YES EaCTOR BLD(L g EL.290'-F ESSDsYlat YES ESSENTIAL YES ESSENilmL EE-67D NO ES D rtal. YES Essosttat TES 9 MlUR S HERp 8 H0tp Bar.PnOf YES M 8 HOLD 6N Ont. PmO( enT. Pact ent.Pacg YES g,y, ,o,tR NUE gg 880pmaL YES NORMAL NONE* N0fMmL NO es0RDM. NO NORMAL YES E8CNIN 2v994PStC ACCESS PATH G4.Y ESSENTIAL YES ESSOffM YES ESSENT1mL NO ES!KNital YES ESSEMital YES EE* .- .
Raf.PmOC N OmT.PmOC YES car. Pact YES .M YES . ent. Pack enT.Pacu 'OE NtpMat. YES ~ NtpMal NipdEe N0pteal NO MORMmL 3s0 peRMmL YES NWC ESSENilat YES E{Tm ESSENT1mL YES ESSDITM NO ESTuttal YES ESE Nrtal YES ae . . . Baf. PaDL eni.PaOC YES YES . . ShT.PnCE enT. Pack YES NODE est. PaCR . NDRMAL YES MORMmL NUE* NORMAL NO edORMfL 00 0 NORMAL YES 2YBB-UPSID I Skg- E310silmL YES ESsostNL YES ESSENT M NO ESSEwitas YES EE-67N ESSDettal YES 8 Belm 8 69UR Bar Pact 'IUT . Bn F. P6 .YES 8 MRR YES S MULF S HotM ear. Pack env. Pack TES car.Pacu NONE e titWMat. LIGNil80 IN EACTOR BUILDING IS POWEND FROM PLANT EMERENCY POWER DrSTRImlfitM SYSTEM. OURfMG LOCA. THIS NON-iE LICHT!*G SYSTEM POWER IS TRIPPED si see scCiDDef Siment -
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9 [ACHMGMf- 8 I ACCESS ROUTE TAKEN BY OPERATOR FROM CONTROL ROOM TO UPS i ROOM IN NORMAL SWITCHGEAR BUILDING ON 8-13-91 l 1 The following route was taken by operator from control room to go to UPS room in switchgear building to j transfer alternate power source to UPS units ; ] Operator left the control room EL 306 through south l door and proceeded to west. Then he turned north along ! the corridor on the westside of the control room. Then he exited the control room building through north west door . EL 306 to Auxiliary building. He then took the stairway l just south of the elevator to go to EL 261. Then at EL ; 261 of Auxiliary building, he proceeded to south and entered the corridor ( Electrical equipment Tunnel) . From l the corridor he entered the normal switchgear building EL 261 and proceeded to stairway located in the center of the building (West half) down to EL 237 where the UPS I units 2VBB-UPS1A, 1B, 1C and 1D are located. He then transferred the UPS power to maintenance power source. After restoring power to the above UPS units, the operator proceeded to UPS 2VBB-UPS1G via the door on the east end of the room, went south down the hall, through ! the door on his left (eastside) and entered the control ! building. He then took the stairs down to EL 214 where f UPS 2VBB-UPS1G is located and transferred the power to l the maintenance power. ) 1 l m p % i l f p . g . [cA BMM L ) t x 7 M se l
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TRAIN C - 2 CEC 4'NL627 FEEDWATER CONTROL PANEL 2 CEC-PNL612
GE Industrial WYh(MM&7 {Q & Power Systems l- PA GE_L of 2 l ItYt" 02**"for Ser nce: Oggime? e
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t NIAGARA MOHAWK POWER CORPORATION cc: NIAGARA MOHAWK POWER CORP. NINE MILE POINT NUCLEAR STATION 1 l UNIT #2, GENERATOR #180X632 R. Abbott ! l GENERATOR INSPECTION - POSSIBLE N. Kabarwal l PHASE-TO-PHASE FAULT M. McCormick l GENERAL ELECTRIC COMPANY i L. Jordan (37-3) l August 28, 1991 W. Judd ! S. Kolb l R. Smith l W. Turk Mr. Anil K. Julka NIAGARA MOHAWK POWER CORPORATION l 301 Plainfield Road I North Syracuse, New York 13212 - Dnar Mr. Julka: Due to the August 13, 1991 failure of the phase B step-up transformer on Nine Mile Point Unit #2, General Electric Generator Engineering recommends performing a thorough visual inspection of the generator stator end winding support system at the next convenient opportunity. The inspection should include all accessible components of the stator end winding support system, including stator bar end arms, blocks, ties nose rings, and outer axial supports. This inspection should be accomplished by a GE Generator Specialist trained to detect the potentially subtle indications of damage. The above recommendation is based upon the possibility of l phase-to-phase generator short circuit currents through the failed transformer as high as 5pu. The initial. recommendation for the immediate generator inspection considered the possibility of higher l currents, resulting in several times greater end winding forces. l Physical evidence of high current forces at the transformer low side was the primary driver for this recommendation, since measurements of generator currents were not available. Our engineers continued to review the limited data available and subsequently concluded that currents high enough to do probable damage to the generator were not j likely. This conclusion was reached primarily by considering a measurement of depressed generator voltage during the incident, inferring generator currents, and specific capabilities of the generator design. I
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A Tf 4M Mf / 0 ( W46 %dF 3,,,. Pcge II Mr. Anil K. Julka August 28, 1991 i Should you have any questions regarding this recommendation, . please contact me. l
<Very rul yours S
0 J eph i i
. Kirhch %\
Ma.ager Enginehring Services
/ Pow'er Generatioh Services ~SfRACUSE OFFICE ,
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